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PROCEEDINGS OF THE
CALIFORNIA ACADEMY OF SCIENCES
February 15, 1977
Series 4, Volume 41, Number 1, 123 Pages, 45 figures
THE OSTEOLOGY, CLASSIFICATION, AND RELATIONSHIPS OF THE EEL FAMILY OPHICHTHIDAE
eo John E. McCosker
Steinhart Aquarium, California Academy of Sciences San Francisco, California 94118
CALIFORNIA ACADEMY OF SCIENCES/GOLDEN GATE PARK/SAN FRANCISCO
February 15, 1977
Series 4, Volume 41, Number 1, 123 Pages, 45 figures
THE OSTEOLOGY, CLASSIFICATION, AND RELATIONSHIPS OF THE EEL FAMILY OPHICHTHIDAE
By John E. McCosker
Steinhart Aquarium, California Academy of Sciences San Francisco, California 94118
ABSTRACT. A classification of the genera of the apodal family Ophichthidae is proposed on the basis of internal and external morphology, with particular emphasis on osteological characters, Specimens of 89 ophichthid species from 44 genera and comparative material from ten other apodal families were prepared for osteological examination, usually by a trypsin-based staining and clearing technique, and critically compared. Forty-nine ophichthid genera are recognized and are distributed among six tribes in two subfamilies. Diagnostic characters for the recognition of genera include the shape and condition of elements of the gill arch and hyoid arch, number and placement of branchiostegal rays along the hyoid, sus- pensorium elements, neurocrania, dentition, pectoral girdle elements, cephalic pore patterns, lateral line ossification, fin placement, and morphometric characters. The Ophichthidae are defined on the basis of their numerous overlapping branchiostegals, supraorbital canals united by a transverse commissure through the fused frontals, first and second epibranchial interconnections, absence of a palatine, and the separation of the pterygoid from the vomer. A monophyletic origin of the family from a congrid-like ancestor is proposed. An evolu- tionary history of the Ophichthidae is suggested, in which the subfamily Myrophinae has separated into two tribes and the subfamily Ophichthinae has radiated into four tribes. The validity of the family name Ophichthidae is discussed. The family names Ophisuridae, Myridae, Myrophidae, Muraenichthyidae, Echelidae, Neenchelidae, Aoteidae, Acanthen- chelyidae and Sphagebranchidae are synonyms of the name Ophichthidae. A comparison is made between an ophichthid classification based primarily on osteology and the previous classification, based primarily on external morphology. The results of two computer-pro- grammed classification schemes of species relationships within a single tribe are compared with a classification developed using traditional methodology. Alternate hypotheses are pro- posed to explain the log-normal inverse relationship between genera and the distribution of species among genera in the Ophichthidae.
CALIFORNIA ACADEMY OF SCIENCES/GOLDEN GATE PARK/SAN FRANCISCO
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TABLE OF CONTENTS Page
LOST? OOTP [PUGS ae a a Ee oes ee 5 LUST OE WBA Se an ee a ee ee Se ee eee ee 6 PNGIIN ON IEEID GNA EINGTIS seat oe eee a ere ee ee A ees ee ee 7 DONTUTRCC ET SATION i Sek ni on a Ro gn oe 9 CGT rel etcetera re Ne ON RR a RPS 2 a ei mn eas Le et 9 ISKOnVRO te © Piicehttni clan Glass iit Gell inp eeaea eee eEE 10 Valli ditwaotastineratimilvadNalnn ees sons see ee ee Se Ses 10 @steologicaleStuclesmotmthie © point Glivtl nical esses eee ee ee 11 Fetal! SwAROMMNVinMNY Cn We (VOM AMM MCNS: csc ses pence aracnoeasaeiteleennassecnqeecereeenens 12 SVMOPSISMm Olen © oli Cine en Glas SI fill Galt © meee eae 13
VAT EAT at @) DB) S prereset eect ae eee cen kN dot AU cers. Seta we ee Lee 2 eens Neuere ae ee Ree 14 AXON OMiLGe NIETO Seren 2: ae eee ee Seen ne te ee eee 14 ING) ON RERITE NTI TVS mae se ee ip a eg al ak ee ie mere ae ree Ew Be Terre ee eee nr do 14 INMare iia Summ sxcel I © Cl te sects cers re cor Sk nee nce Ran ae oS cee ne aE 115 Statist calle NA Cth © CS pe ccseeretas ee. elec nee cece Se ee oe ee ence a eee 16 OSTIEOLOGYAAN DOIN Gail @ INAS AINA GTI @ NAN eee ee ea 17 INQUITROXCTITUI I eI Ns A ep ae Ae A es eR, SRT WR EB Oe tare SP ae etek ew OD 18 SUSDEMSOnUin Mpa) Cala Stes eee eee ees oe eee ei ewe td eae ee tala eee ed eee 24 (OVOVSTRCUNLETE SYSU TRS eee a Ea en SP RM oe CO ee te AY 26 FLAVONIG!" AVC) OF IEE UI a a Ea REE ele Fa he ee a ne ee A Gee be ee ee ee 28 GrTTBRPAN Gin Steet acta nee cere ne eke Ese ee SE ee we eet ne nd Pes ee SK NE 32 Recto all Gite) Cie sere tek oom crete Bec Mee EN Ot ARG An ony ec ezcninrt se ceed ewes MAUR 33
TRAN pall Same SV-S1CG tae see nce eaten Noe sec Se eee OLDEN Ee EP RCE NN ied SO SO ROE ee ER 36 PSE) SIRS EXC CYS Bae ee tea a aS te Ee EN Re eh Ses eR erent 42 (@alliclalleeS Kel ete ri ee ne ee cee ce eee ee eae ee eo 45 NSCS TNT M CO NY ee a ee ee ee te eee 48 TAUOINIOUNAN LBS ater AEE RE re ONE rns = ed AER Oe 48 OsteolosicalsDetinitionmotmtiney. © fo lnt cht lnc ele een eee 49 AnalviticalakeyatonthenGemetanot © pln htin cl ele eee seen eee en eens 50
| EIUTOY Se GEA SH ST ae eS ee RES ONE en Oe eee Ne ee eer ne ee 56 Subfamilial and Tribal Diagnoses and Generic Descriptions ........................---------------- 57
S Ura fala Lame VAN @ PIMNIN a Cisse sete Ea cern cea eee cen ie aan See seed Sco Semen 57 Tribe Benthenchelyini (Genera are listed alphabetically within each tribe) -....... 57,
Tithe cae WANT POINT lies sees ee eee ie ead ee Re Se ect eine Ree Ve ee 57 Sulfate @ pln clnthinaes<-cee.ccese ac cece ee oe cee en ers o ee Se cere ec ese ee 62
al ftai to eee @all Hehe bn rps ae ee ee ee ee ee ee DE Eo 62 inibemspiare bray Ghitiniee see ere te see tesa 2 ctor ee ie cael 2 eee 64
Miriam aS Gel ml Glinitih i Id gaa ea ae ee eke Fe OF We cee ee Nt eee eee 70
Wtloves CO fool pitied ni nin] Seen aes ene Bt ae eee eo LE ne ae ee Perea eee 73 GompanisonmwithmeneviOUSn Glass Calti@ mSy esses eee eee eye 85 ENWOILUNTIOUN (Ol TRIE COPRIICTRINRIIOYNE aoc ercnes ase ecneceenc ss Sesgee epee perpen Bop ee eS DO SEE EEE 85 Relat Oms tio m CO mOthne ray A tne Ulli rrr Siemens eee eae era nnn 85 EWOMUUNCO LH) AOMATUL MMM) tA COV TCT nyt CLS) ee 86 MMVIROFOLMIID ine! TEMG MEMEIMITDN — co sececccenne conecee eee seece ener ecm eee Rs aeneaerecerer pRoDAD HOSS EEEOSECEEEBEES 88 COWS RTSI LU MMUMLAN = ack eas es eer eee NO oe cer yt UC PCR er eee eee eee ete sks 89 Sita ge bral clini iif eaten ee eee ene ete noo ee eee ee tee ER ree 91
Beals earl GIG ip meee erecta meme nc tines ete eee Pi hy Chel Cle a cee eat Wee A he ad 94 Gallechyel\itriiiameteen erate eee hes Nae Deer: oe a Td oo ea ee Be ete 94 ZOOGEOGRAPHY AND COMMENTS ON OPHICHTHID SPECIATION ..............-.--...--------- 96 [LUPTTELRSVN TIRE (CTE Yo rey a AS ace aE ae Sa sad cn ER SR Ie a, ue eee oe, 101 AB KES eee ete ir, ener A RG Ser ee oe Ao mW ee a eee Har ek ee Sea 108
PROCEEDINGS CALIFORNIA ACADEMY OF SCIENCES
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LIST OF FIGURES
An Early Illustration of an Ophichthid, presumably Ophisurus serpens .................- NedrocraniUimmotm © polaiclatlnusweZ Ojo no Gliliga seen eee en NetnocraniUnn nots © a hniGiathtiSiez Op lO Ginliigesesae senses tenner Neuro Granite Bem thiernGin@ isin Gel itil irene eae eee ne en cE ES NG unOGraniUinmn iO fil VV{i@ Toil Sav cli ames ees En oo Neuro cranium One Meira eniliGithnySirGinilenmS 1S. esssssee teen ence en ee ee NeurocranUmmotm @alll@Gineliysiiimalrinp © nali Us apenas eee ane nee ee ee eee Neuro craniUinmoteaGiitinyaoUrsies eC] a\Gii@ [a Simsesseeere eee arenes eee NeURocAniuinn @ir SWiGiodminWS [OOMMIUS ccecee eer cece eee eee rsa eeeeeSeeeeee INEUKOcraniUMmOneBascaniGhth/Sm palmar C SiS esse tes tes scee eee eames ae NGUROGMIUIIN Cir IMAM AIS: SSVSTRUITWIS xcesseeccese cree ese c cence eeee coe cer eno a cea eeE Ree Re eem = HES aon nEnee @xoliths of Several’ @phichtinid Species EA ae Boe rin Se See Fleadmskeletommons © piGhitinUsiez OO © Cilia eeeeeea eee ee neon E Suspensonum) and jawsnot Ophichthus Zophochiin sss RightsPostonbital/ Series) of BrachySOmoOpinis) SAUMOPSIS, cess eee ee een Maxilla-VomensApposition: of Severall @yolniehnthyics wes cee eee Hyoid Arch and Branchiostegals of Ophichthus zophochir, an Ophichthine,
ANG eel ea Gitay Sin Gln C1aSTSPaclan NAW/© [Ohi Cleese eee ec GillArcheskeletonmotm© piiiGitinustez.o in @ Cin aes ene ee Pectoral Girdle of Various Representative Ophichthines .................--------------0---00--- Pectoral Girdle of Various Representative Myrophines .............-..------:---------0000100+++= GephaliesRateralissSystembpanGeASSOGlatec | BOnes messes eee Lateral Line Ossicles of Representative Ophichthines .......................2.-.0--00ecceeeeeeeeeeeee Lateral Line Ossicles of Representative Myrophines .................-.-.--------------------------+
Cephalic Pore and Surface Sensory Papillae Development in Two Ophichthids .... Anteriormost Five Vertebrae of the Type Genera of the Tribes of Ophichthids .... Trunk and Caudal Vertebrae of Ophichhtus zophochir ...................-.--.-..2200--+-------+- Caudal Skeleton of Ophichthus zophochir ................-.......------- sate 5, SONIA ei et Oe GaicaleSkeletonmo te Vino phils aval Cymer Comparative Anatomy of Congrid and Ophichthid Digestive Tract and
(GES. “BB V0 Kol eir Re ee ok A a, a as ae emetic a ek dill pe gee 41 hw Wn BO re aa
Vomer, Maxillae, and Pterygoid of Ahlia egmontis and Myrophis vafer ................ Diagrammatic Representation of a Species with Well Developed Head Pores ...... Representation of Underside of Callechelyin Smouts .................22.--200000-222222000e--eee-e= Diagrammatic Representation of Posterior Trunk Vertebrae ................220.-00.---------- Diagrammatic Representation of Head and Pectoral Fins of Two Ophichthins ...... Diagrammatic Representation of an Ophichthin with a Fringed Upper Lip —.......... @©penculaneSenlesoteMiyropmismVvaret ss. = eee ee en Pe ee Proposed Evolutionary Relationships of Ophichthid Tribes —.................0222000.-...---- PROPOSE MEV. UETO MO itiatin Cal VAN TO [olin ele eee eee Nn RrOPOSEEEVO]UTO MMO Tate © knit Ghat nna eee ee ae ee sue en pS BLODOSEASEVOUTLONMOfatheMs Pliage ali Glniliiimeesemees seers eee BrODOSCGMEVOUTONMO fe tiveN Bas Gali Glitnir eres eee PROPOSCU MEV OUT ONMmOl mtn em alll Ec lne lly, iinet eee Phenogram of the Relationships of the Callechelyini, Using Program WVGM ......
Interrelationships of Species Groups of the Tribe Callechelyini, as Defined by PORN LEO © OI ES cee ne Sen salar Sean re Oe MN MeN RINE NTS ay eee eeaito Distribution of Species Among the Genera of the Ophichthidae,
Gobiesocidae and _ Salariini
6
SERIES 4, V.41, #1 McCOSKER — EELS
LIST OF TABLES
Table Page PD eMtitOnmOimthem Gem enaeotin© plat cliche epseceee ee ease eee tenes eee snes 108 2 Number and Location of Branchiostegal Rays of the Species of the Ophichthidae .... 109 See GilleArcheGonelitio nny th yey © po ai ltl rea Crees eee etme ns enn seen 110 aL Gill “Aely Geommvaliittiormy flim: me IMAGO Son cere eee ee CeCe 111 5 Lateral Line and Cephalic Pore Conditions in Ophichthine Genera and Subgenera .. 112 6 Wereorll Coume Or Waltouws Wyolnichntimicl SlxXheS .sceesecs access cage ceccenennonccosenseseeseons Ms 7. ‘Gharacteristics of the Ophichthidae and Related Eel Families... 116 8 Morphological and Meristic Characters of the Species of the Callechelyini —........... 7, 9 Characteristics of the Species of Callechelyini Used in Programs REGROUP
PATI) GR VIN Gt ANS ose ta steel NC 2 Sr ec SA Sao J we nyu ee Se, Seen ne 118
10. Wistribution“of Certain Ophichthid) Gemena: .....22. 2 cen2-05s2-cece ace oe cece 119
PROCEEDINGS CALIFORNIA ACADEMY OF SCIENCES
ACKNOWLEDGMENTS
The majority of this work is from my doctoral dissertation done at the Scripps Institution of Oceanography, University of California, San Diego, under the direction of Richard H. Rosen- blatt and Carl L. Hubbs. | sincerely thank Profes- sor Hubbs for his advice and guidance through the capricious nuances of zoological nomencla- ture, and Professor Rosenblatt for his invaluable advice, encouragement, and patience throughout the duration of my graduate studies.
| wish to express my gratitude to the following individuals who have made various specimens available: Marie-Louise Bauchot, Paris Museum; Jacques Blache, Centre ORSTOM,; James E. Bohlke, Academy of Natural Sciences of Philadelphia; Peter H. J. Castle, Victoria University of Welling- ton, New Zealand; Lev Fishelson, Hebrew Uni- versity; John E. Fitch, California Department of Fish and Game; Warren C. Freihofer, then of Stanford University; Robert H. Gibbs, Jr. and Robert H. Kanazawa, National Museum of Natural History; William A. Gosline, then of University of Hawaii; Naercio A. Menezes, Universidade de Sao Paulo; Hans Nijssen, Zodlogisch Museum Amsterdam; John R. Paxton and Douglass F. Hoese, Australian Museum; John E. Randall,
Bernice P. Bishop Museum; Tyson R. Roberts, Museum of Comparative Zoology, Harvard Uni- versity; C. Richard Robins, University of Miami Marine Laboratory; Margaret M. Smith, Rhodes University; Enrico Tortonese, Museo Civico di Storia Naturale, Genova; Boyd W. Walker and John Bleck, University of California, Los Angeles. | am particularly grateful to William N. Esch- meyer and the staff of the California Academy of Sciences for making the extensive and critical material from the George Vanderbilt Collections available to me.
Thanks are also due to the following individ- uals: Ira Rubinoff and the staff of the Smithsonian Tropical Research Institute for assistance during my tenure as a Smithsonian pre-doctoral research fellow; Edward W. Fager and John H. Wormuth for assistance with computer programs; students and colleagues at Scripps Institution, and in par- ticular Joseph F. Copp and Donald M. Dockins, for aiding in numerous ways; Richard H. Rosen- blatt, Carl L. Hubbs, Robert R. Hessler, and Peter Paul Vaughn for their critical reading of my dis- sertation; and my wife, Sandra, for her help and encouragement.
SERIES 4, V.41, #1 McCOSKER — EELS
SERPENT MARIN.
UMMA IFEOES 7570, i 4 VILL —oe wo MCU TET poe Ui eS: / ye tH LCC Gay, Sk < RAY 1 "ag, —\ IE eS DL uyetae 4 = gat nay sete Se SR Lhe. cAS-. ‘J S % ” Lo AS 5 2 % WR J, = P ; 4 SR 2 3 W pp ee , wee Zz E Wir rss ‘WS if? E oe, A > ince s os VAM \S= OB Ps 1 Fy Wi If gE 5 =.= Zé ORT) aN IX: = Aa Bs : 5 A z N ~ 2 ° as 7 Se ; \ ye £[F aN LE AG * Za w= BS Af, e Ffg= \\ = FX SS — ' {! 1, 4, serpens,
An early illustration of an ophichthid eel, presumably Ophisurus
Figure 1. from Mattioli’s Commentaires (1568).
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THE OSTEOLOGY, CLASSIFICATION, AND RELATIONSHIPS OF THE EEL FAMILY OPHICHTHIDAE
John E. McCosker
INTRODUCTION
General
The Ophichthidae comprise a large family of mostly fossorial eels limited to continental shelf depths of all tropical and subtropical oceans. The Ophichthidae contains more than 200 species here distributed among 49 genera, representing perhaps the greatest diversity of anatomical spe- cializations within a single apodal family. The resemblance of many ophichthids to snakes has earned them the common name of ‘‘snake-eels,’” and along with the morays, have evoked many sea-serpent legends among tropical coastal peo- ples. Perhaps the earliest illustration identifiable as an ophichthid (fig. 1) was that of Mattioli (1568) p. 388, probably based on an adult Ophi- surus serpens. The first described ophichthid species, Muraena ophis, was the second apodal fish in Linnaeus’ Systema Naturae (1758).
The taxonomic treatment of the Ophichthidae, and of apodal fishes in general, has been in con- stant flux since the eighteenth century, and only within the past two decades has a coherent con- cept of the Ophichthidae become realized. Pre- vious theories of the interrelationships of ophich- thid genera have been based on such trivial char- acters as fin position, dentition types and colora- tion. It is now generally accepted that the osteol- ogy more conservatively reflects the phylogeny of a group and is less affected than external morphology by minor evolutionary adaptations. The unsatisfactory state of the classification of the ophichthids has been recognized by numer- ous authors (Myers and Storey, 1939; Myers and Wade, 1941; Gosline, 1951a; Smith, 1964; Rosen- blatt and McCosker, 1970; Robins and Robins, 1971; Castle, 1972) most of whom have con- cluded that an osteological revision of all in- cluded genera was necessary for a proper under- standing of the family. The aim and scope of this study have been directed to that objective.
10
History of Ophichthid Classification
The 218 years since Linnaeus’ (1758) descrip- tion of the first ophichthid species have witnessed a plethora of generic and specific names applied to the Ophichthidae. The first generic name properly applied to an ophichthid was Ophich- thus (Ahl, 1789), which should more properly have been written “Ophichthys’”. The emenda- tions of Ahl’s generic spelling by subsequent authors have resulted in confusion over the gen- eric and familial names. This problem was briefly treated by Gosline (1951a: p. 298) and is further illuminated in the following discussion.
The treatment of apodal taxonomy was in con- stant flux during the eighteenth and nineteenth centuries, which accounts for much of the lack of uniformity in nomenclature. Swainson’s (1838) treatment of the eel-like fishes was based largely on Cuvier’s work (1817), and was the first at- tempt at an arrangement of the eels into family groups. Swainson (p. 215) designated the ‘“Mur- aenidae (as) having two branchial spiracles in their ordinary position, and the Sphagebranch- idae, or sea eels, where the branchial spiracles are either close together or united into one.” Confusion ensues on the following page where the family name Gymnarchidae is apparently con- sidered synonymous with the Symbranchidae, and further evidenced in his discussion (p. 218) of the gill openings, by his statement that ‘‘among the Gymnarchidae, or sea eels, for instance, they are close together and united under the throat as in Sphagebranchus.”” Swainson divided the Mur- aenidae into two subfamilies, the Anguillinae and the Muraeninae, both of which contained species now known to be ophichthids. McClelland (1844) realigned the apodal classifications of Swainson and Cuvier and created the family Ophisuridae to include eels with a rayless caudal contain- ing the genera Leptognathus (=Ophisurus), Ophi- surus, and Ophithorax (=Ophichthus). Kaup (1856a,b) disregarded most of McClelland’s classification without comment, but did retain the name Ophisuridae. Kaup divided the apodal fishes into two ‘sections’. These were the Cryp- tomycteres (containing only the Ophisuridae) which included those eels with labial nostrils, and the Phaneromycteres which contained all other apodal families. The ophisurids were divided into three subfamilies, the Ophisurinae, the Sphage- branchinae, and the Myrophinae (containing Myrus, Myrophis, and Muraenichthys). Bleeker, in his Systema Muraenorum Revisum (1865), rec- ognized the family Ophisuroidei and considered
SERIES 4, V. 41, #1 McCOSKER — EELS
the Myrophinae (as Myriformes) to be a subfamily of the family Congroidei. Ginther (1870) con- siderably revised previous classification by plac- ing the majority of the known eels into a single family, the Muraenidae, which he divided into ten ‘‘Groups’’. The Ophisuridae of earlier authors was divided into two groups, the Ophichthyina containing those species with a rayless caudal [comprising the genera Liuranus (sic) with a single species and Ophichthys with at least 78 species], and the Myrina containing those with a rayed caudal (comprising Myrus, Myrophis, Para- myrus, Chilorhinus, and Muraenichthys). Gwtn- ther’s groups were elevated to family rank by Jordan and Davis (1891). The Myrinae became the family Echelidae (Jordan and Davis considered Myrus a synonym of Echelus) and the Ophich- thyina of Giinther (actually, the Ophisuroidei of Bleeker) became the Ophisuridae. Uncertainty concerning the synonymy of Myrus and Echelus resulted in the changing of the name Echelidae to Myridae by Jordan and Evermann (1896) and by Jordan and Snyder (1901). The family name Ophichthyidae, derived from Gunther's Ophich- thyina, first appeared in Jordan and Evermann (1896). The authors rejected the name Ophisuri- dae and considered Ophisurus a synonym of Ophichthus.
Validity of the Family Name
Confusion relating to the spelling of the Ophichthyidae with a “y’’ relates to the correc- tion by earlier authors of Ahl’s (1789) spelling of Ophichthus. The generic name is from the Greek
re PF , meaning snake, and ixvovys, mean- ing fish, and would more correctly have been written Ophichthys. Bleeker, Gunther, and other classicists emended Ahl’s generic spelling (see Jordan and Gilbert, 1882), but Jordan and his later co-authors returned to Ahl’s original spell- ing. The retention of the original spelling of the generic name but the usage of the emended fam- ily name is illogical, and according to the Inter- national Code of Zoological Nomenclature, in- correct, as Gosline (1951a) has pointed out. Most recent authors, with few exceptions, have used “Ophichthidae”’ and ‘“Ophichthus”.
A serious difficulty however exists, concerning the earlier family names proposed by Swainson and by McClelland. The inconsistencies in Swain- son’s usage of Sphagebranchidae would invalidate it as a family name. Although Sphagebranchus Bloch (1795) was then a valid genus and properly an ophichthid, Gymnarchus, a gymnarchid, was
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later shown not to be an apodal fish. The prob- lem of recognizing McClelland’s usage of Ophi- suridae was avoided by Gosline who stated that “whether or not Ophisurus is a valid genus is a moot nomenclatorial question. Consequently | prefer not to use for this family, at the present time, the little-known and possibly invalid name Ophisuridae.”’ The logical solution to this nomen- clatural dilemma seems to be the invoking of the plenary powers of the International Commission on Zoological Nomenclature. The suppression of the rarely used name Ophisuridae in favor of the universally recognized name Ophichthidae would clearly be in the interests of stability.
Osteological Studies of the Ophichthidae
Regan (1912) was the first to attempt an osteo- logical definition of the Ophichthidae. Most im- portantly, his emphasis on the fused frontals of the ophichthids, congrids, and relatives has re- mained as a fundamental character in our con- cept of eel evolution. The other osteologicai characters identified by Regan (‘‘caudal vertebrae with transverse processes” and ‘‘maxillaries articu- lating with ethmoid near the end of the snout’) only described certain members of the family. His separation of the congrids from the ophichthids, on the basis of their long and slender rather than vestigial neural spines, was also an important ob- servation. Trewavas’ (1932) apodal classification scheme followed Regan’s characterization of the ophichthids. For nearly two decades, subsequent ophichthid studies dealt only with superficial characters. An exception was that of Myers and Storey (1939) who noticed the overlapping of the branchiostegal rays in ophichthid species. They pointed out that these rays are similar to the “jugostegalia’’ described by Parr (1930) in echelid eels. On that basis, and other external morpho- logical similarities, Myers and Storey suggested that the Echelidae might be merged with the Ophichthidae.
Gosline (1950, 1951a, 1951b, 1952), in a series of papers, analyzed the species referred to the Echelidae and the Ophichthidae. His osteological study of Kaupichthys diodontus (1950) demon- strated that its osteology precluded its inclusion in the same family with Muraenichthys cookei. He found (p. 312-314) that K. diodontus differs in having sutured frontals and non-overlapping branchiostegal rays, as well as several other char- acters which later proved to be non-definitive. Lacking a specimen of Echelus myrus, Gosline was unable to further define the Echelidae, but suggested that species of Myrophis and Muraen-
11
ichthys might be referred to the Ophichthidae, to comprise the subfamily Myrophinae, on the basis of their “basket-like arrangement of the numer- ous, long branchiostegal rays.” In a following paper, Gosline (1951b) described the osteology of Chilorhinus brocki (=C. platyrhynchus) and related it to Kaupichthys diodontus. He suggested that the external similarities of species of Kaup- ichthys, Chilorhinus and ophichthids are ‘‘the re- sult of parallel evolution and not of close genetic relationship.” His prediction that Echelus, once examined on an osteological basis, would prove to be confamilial with Kaupichthys was incorrect (Gosline, 1952; Bohl ke, 1956a).
Gosline (1951a), in a more comprehensive paper, prepared the first diagnostic treatment of the Ophichthidae. His study, however, was limi- ted to those species occurring in the Hawaiian area and thus did not include several critical genera. He compared the Ophichthidae with the Congridae (primarily Conger), and concluded that the ophichthid conditions are derived from, and more advanced than, those of their more primi- tive congrid ancestors. Two subfamilies within the Ophichthidae were recognized (the Myro- phinae and the Ophichthinae) although osteo- logical differences other than the caudal skeleton were not defined. In a subsequent paper, Gosline (1952) described the morphology of Echelus myrus in detail and concluded that it was refer- able to the ophichthid subfamily which contained Myrophis and Muraenichthys. On that basis he changed the subfamilial name of the Myrophinae to Echelinae. The results of that study did not alter his earlier (1951a) diagnosis of the family.
Subsequent studies dealing with ophichthid osteology followed Gosline’s (1951a) general defi- nition of the family, but amended his diagnosis to include genera that he had not examined. Bohlke (1960) added Pseudomyrophis, and provi- sionally Neenchelys, to the Ophichthidae.In do- ing so, he expanded the familial diagnosis to allow the following: posterior nostrils either lat- eral or labial; maxillary articulation variable in position along the ethmoid; pharyngeal openings of the branchial clefts may be reduced; trans- verse processes of the caudal vertebrae either present or absent.
Nelson’s (1966a) analysis of apodal gill arch conditions found most ophichthids to be ‘‘dis- tinguished in having the proximal ends of the dorsal parts of the first and second arches con- nected through a continuous cartilage, a peculiar- ity not present in any other of the eel families studied.’’ Certain generic lineages were identified
12
on the basis of their gill arch configurations. Nel- son's (1966b) study of the osteology of Neen- chelys buitendijki confirmed Bohlke’s earlier sup- position of its placement within the Ophichthidae. Nelson separated the ophichthids from the con- grids in the following manner: posterior nostril usually opening on the ventral surface of the upper lip; tongue adnate; branchiostegal rays overlapping along the midventral line; supraorbi- tal canals united by the transverse frontal com- missure; neural spines absent. Castle’s (1972) osteological study of Benthenchelys cartieri sum- marized the diagnoses from Gosline’s, BOhlke’s, and Nelson’s earlier works, but did not contribute to or amend their diagnoses.
Familial Synonymy of the Ophichthidae
The Ophichthidae, as currently recognized, in- cludes several families which were until recently considered distinct. The basis and validity of studies resulting in these actions are discussed below.
The family Neenchelidae was erected by Bamber (1915) to contain Neenchelys microtretus, a new genus and species from the Red Sea. It was considered to be closely related to the Mur- aenesocidae as defined by Regan (1912). A sec- ond neenchelid, N. buitendijki, was described by Weber and de Beaufort (1916) from the Indo- Australian archipelago. The family received no further definitive treatment until Bohlke (1960), on the basis of Bamber’s description, suggested that Neenchelys may be related to species of Pseudomyrophis and thus properly be considered an ophichthid of the subfamily Echelinae (sensu Gosline, 1951a, 1952). The collection of adequate material of N. buitendijki and its osteological ex- amination by Nelson (1966b) supported Bohlke’s prediction. Nelson’s (1967) examination of the holotype of N. microtretus confirmed the recog- nition of the Neenchelidae as ophichthids in the subfamily Echelinae (herein considered as Myro- phinae).
The Acanthenchelyidae also belongs in the Ophichthidae. Family recognition was short-lived, consisting of Jordan, Evermann, and Clark’s (1930) elevation of Acanthenchelys Norman. (errone- ously attributed to Regan) to family status, but this was largely ignored by later authors. Randall and Robins (1966) relegated Acanthenchelys to the synonymy of Ophichthus, an action which is followed here.
The Aoteidae are provisionally included in the Ophichthidae. The Aoteidae were first recognized
SERIES 4, V.41, #1 McCOSKER — EELS
as ophichthids by Castle (1967), who referred the single aoteid species to the genus Muraenichthys.
The family Echelidae (=Myridae, Myrophinae, Myrophidae, and Muraenichthyidae), has been a catch-all group with a checkered history. The echelids were considered congrid or muraene- socid relatives by most nineteenth century au- thors. Bleeker (1865), for example, considered the Myriformes (containing Myrophis, Echelys, and Muraenichthys) to be a subfamily of the Congroidei. Kaup (1856a,b) was exceptional in placing considerable importance on the labial nostril condition, and in allying the Myrophinae with the Ophisurinae as a single unit which ex- cluded the congroids and relatives. Twentieth century authors considerably expanded the Myro- phidae (which was to become known as the Echelidae, fide Jordan and Evermann, 1896) to include as many as 22 genera at various times (Schultz and Woods, 1949). The dissection of this large and cumbersome family was initiated by Myers and Storey (1939), and was followed by Schultz and Woods (1949) and by Gosline (1950, 1951a, b, 1952). Myers and Storey noted the pres- ence of accessory branchiostegal rays (the “‘jugo- stegalia’’ of Parr, 1930) in both ophichthids and echelids, but were hesitant to merge the families without an extensive anatomical examination. Gosline (1951a) established the similarities of the two families on an osteological basis and included the genera Myrophis and Muraenichthys in the Ophichthidae to comprise the subfamily Myro- phinae. His subsequent (1952) osteological ex- amination of Echelus myrus resulted in its inclu- sion into the family, and the replacement of the name Myrophinae with Echelinae. The present study has demonstrated that Gosline was correct in considering the Myrophines to be ophichthids, but erred in including Echelus with the Myro- phinae. Although certain authors have continued to recognize a family Echelidae for the forms with caudal rays (e.g., J. L. B. Smith, 1962; Blache, 1968), no convincing arguments have been pro- posed which would merit familial separation. Blache’s (1968: 1501) continued usage of the name Echelidae, with the justification that “.,.nous sommes également, tout a fait, partisan de cette position et nous ne conservons ici, la famille des Echelidae, que pour des raisons arti- ficielles de commodité taxonomique,” is both illogical and incorrect.
Further substantiation of the inclusion of the Echelidae with the Ophichthidae is evidenced in the leptocephalus larval stage. (The leptoce- phalus of Neenchelys has not been identified.)
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Eel leptocephali display evolutionarily conserva- tive features that could prove useful in phylogen- etic investigations (Castle, 1965, 1967), yet the problem of generic and specific identification still remains and has precluded their usage in this study. It is important to note, however, that the morphology of ophichthid leptocephali re- flects the family grouping fairly well. Castle (1965) and D. Smith (unpub. MS) have diagnosed the ophichthid leptocephalus as moderately elongate when full grown, characteristically possessing gut thickenings or loops which usually accompany swellings of the pronephric ducts, conspicuously pigmented with patches of chromatophores which occasionally occur on the head, at various points along the gut, and often on the myosepta, lateral caudal midline, and dorsal and anal bases, and possessing a moderate to blunt tail. Castle (1965: 98) has stated that ‘‘the pectoral remains obvious throughout larval life, probably even in those ophichthids which show loss of the pectoral in the juvenile and adult.’’ Phylogenetic implications at the generic level would therefore be further evidenced in this conservative larval condition if Castle’s suggestion proves correct. For example, his tentative identification of Leptocephalus Mur- aenichthys sp. is based on a leptocephalus pos- sessing a short, rounded pectoral fin (Castle, 1965: figs. 2F, G), not unlike that of Myrophis (Eldred, 1966; Castle, 1965: figs. 3e-f).
In contrast to the above mentioned families, the Macrocephenchelyidae was incorrectly synony- mized with the Ophichthidae. This family, known only from the holotype and damaged paratype of Macrocephenchelys brachialis Fowler, was syn- onymized without comment with the Ophichthi- dae by McAllister (1968: 85). Robins and Robins (1971) have re-erected the family on the basis of a thorough osteological examination of the para- type. They have shown its affinities to be with the Congridae and referred it to the superfamily Congroidea. Macrocephenchelys displays several characters quite divergent from the Ophichthidae, including the extensive ossification of the bran- chial apparatus (yet there is no lower pharyngeal tooth plate), the absence of the transverse frontal commissure of the cephalic lateralis system, and the presence of eight stout branchiostegal rays and a complete palatopterygoid arch.
Synopsis of Ophichthid Classification
The listing of nominal taxa below summarizes the taxonomic conclusions of this study. Full de- scriptions of new taxa and complete generic syn- Onymies are presented later in this paper.
13
Subfamily Myrophinae Tribe Benthenchelyini Benthenchelys Fowler 1934 Tribe Myrophini Ahlia Jordan and Davis 1891 Muraenichthys Bleeker 1853 Subgenus Muraenichthys Bleeker 1853 Subgenus Scolecenchelys Ogilby 1897 Myrophis Lutken 1851 Neenchelys Bamber 1915 Pseudomyrophis Wade 1946 Schismorhynchus McCosker 1970 Schultzidia Gosline 1951
Subfamily Ophichthinae
Tribe Callechelyini Aprognathodon Bohlke 1966 Callechelys Kaup 1856 Letharchus Goode and Bean 1882 Leuropharus Rosenblatt and McCosker 1970 Paraletharchus McCosker 1974
Tribe Sphagebranchini
Achirophichthys Bleeker 1865
Apterichtus Duméril 1806
Caecula Vahl 1794
Cirricaecula Schultz 1953
Hemerorhinus Weber and de Beaufort 1916, incertae sedis
Ichthyapus de Barneville 1847
Lamnostoma Kaup 1856
Stictorhinus Bohlke and McCosker 1975
Yirrkala Whitley 1940
Tribe Bascanichthyini Allips McCosker 1972 Bascanichthys Jordan and Davis 1891 Caralophia Bohlke 1955 Dalophis Rafinesque 1810 Ethadophis Rosenblatt and McCosker 1970 Gordiichthys Jordan and Davis 1891 Leptenchelys Myers and Wade 1941 Phaenomonas Myers and Wade 1941
Tribe Ophichthini
Aplatophis Bohlke 1956
Brachysomophis Kaup 1856
Cirrhimuraena Kaup 1856 Subgenus Cirrhimuraena Kaup 1856 Subgenus Jenkinsiella Jordan and
Evermann 1905
Echelus Rafinesque 1810
Echiophis Kaup 1856
Elapsopis Kaup 1856
Evips McCosker 1972
Leiuranus Bleeker 1853
14
Malvoliophis Whitley 1934 Myrichthys Girard 1859 Mystriophis Kaup 1856 Ophichthus Ahl 1789 Subgenus Ophichthus Ahl 1789 Subgenus Microdonophis Kaup 1856 Subgenus Centrurophis Kaup 1856 Subgenus Coecilophis Kaup 1856 Ophisurus Lacépéde 1800 Phyllophichthus Gosline 1951 Pisodonophis Kaup 1856 Pogonophis Myers and Wade 1941 Quassiremus Jordan and Davis 1891 Scytalichthys Jordan and Davis 1891 Xyrias Jordan and Snyder 1901
METHODS Taxonomic Methods
Osteological examinations, whenever possible, were based on entire stained and cleared speci- mens. Rare specimens and holotypes were studied by gill arch removal and radiographic examina- tion. Radiographs were prepared using a General Electric 40 KV x-ray unit and Kodak Industrial Type M film. Radiographs were either examined under a dissecting microscope or from photo- graphic enlargements. Stained and cleared gill arches or entire specimens were prepared using the trypsin-preparation method of Taylor (1967) and, in certain instances, the modifications of Miller and Landingham (1969). Neurocrania were prepared by dissection, soaking in a 5-7 percent potassium hydroxide (KOH) solution to remove the flesh, and staining in an alizirin bath. Sutures along the dry skulls became more apparent dur- ing examination when painted with pure glycerin using a fine camel’s hair paint brush. Certain skulls were disarticulated in a 7-10 percent KOH solution to better identify certain sutures. Draw- ings were made using a camera lucida attach- ment on a Wild dissecting microscope.
Gill arch terminology is that of Nelson (1969). Bone terminology follows that of Asano (1962) with certain modifications that are identified in the section dealing with bone complexes.
The following measurements, used in the gen- eric key and descriptions, are defined as follows:
Head length. Measured from the snout tip to the posterodorsal point of the gill opening.
Trunk length. Measured from the posterodorsal point of the gill opening to mid-anus.
Tail length. Measured from mid-anus to the tail tip.
SERIES 4, V.41,#1 McCOSKER — EELS
Inclination of the suspensorium. The suspen- sorium is considered to be ‘anteriorly inclined’’ if the angle formed by the midlines of the hyo- mandibular and the mandible (when the mouth is closed) is greater than 90°. If the angle is less than 90° the suspensorium is considered to be “nosteriorly inclined’. This measurement is some- what subjective, and made either from radio- graphs or observations of stained and cleared specimens under the dissecting microscope.
All fish lengths are listed as total lengths. Gen- eric descriptions and diagnoses were based on adults unless otherwise stated.
ABBREVIATIONS Anatomical Abbreviations
A-anus; an-anterior nostril; AR- anal fin ray; B, - first basibranchial; BO - basioccipital; BR - branchiostegal ray; BS-basisphenoid; Cy, - first ceratobranchial; CE-centrum; CH - ceratohyal; Cl-cleithrum; Co-coracoid; CTP-transverse pro- cesses of caudal vertebrae; CX - cartilaginous ex- tension of terminal vertebra; D-dentary; DFO - dorsal fin origin; DR - dorsal fin ray; E- eyeball; E, - first epibranchial; EH - epihyal; EN - epineur- al; EO - epiotic; ET - ethmoid portion of premax- illoethmovomer; EX - exoccipital; F - frontal; GB - gas bladder; GH - glossohyal; GO - gill opening; H - heart; H: - first hypobranchial; HA - haemal arch; HH-hypohyal; HY-hypural; HYM - hyo- mandibular; I - intestine; I, - second infrapharyn- gobranchial; IM - intramuscular bone; io - infra- orbital pore; IO - interopercle; L/D - relation of length to depth; LL- lateral line; LP - lower pharyngeal tooth plate; MX - maxilla; N - nasal; NA - neural arch; NS - neural spine; OP - opercle; OR - orbit; P- parapophysis; PA - parietal; PAS - parasphenoid; PD- pneumatic duct; PG - ptery- goid; PL- pleural rib; pm - preoperculomandibu- lar pore; PO-preopercle; pop - preopercular pore; por-postorbital pore; POR - postorbital; PR - pectoral fin rays; Pt-pterygiophore; PT - pterotic; PTS - pterosphenoid; Q-quadrate; S- stomach; SA- sagitta; Sc-scapula; SCI - supra- cleithrum; so - supraorbital pore; SO - supraocci- pital; SOC -supraoccipital crest; SOP - subop- ercle; sp-surface sensory papillae; SP - sphen- otic; stp-supratemporal pore; tp-temporal pore; UH - urohyal; UP - upper pharyngeal tooth plate; V - vertebra; VO - vomer.
Distributional Abbreviations
EA -eastern Atlantic; EP-eastern Pacific; IP - central and Indo-west Pacific; M - Mediterranean; WA - western Atlantic.
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Institutional Abbreviations
The following abbreviations are used in reference to material examined:
ANSP - Academy of Natural Sciences of Philadel- phia; BPBM - Bernice P. Bishop Museum; CAS - California Academy of Sciences; DANA - Carls- bergfondets DANA-Ekspeditioner, Marinbiologisk Laboratorium Charlottenlund Slot, Denmark; IA - Australian Museum at Sydney; LACM - Los An- geles County Museum; MCZ- Museum of Com- parative Zoology, Harvard University; MNHN - Muséum National d’Histoire Naturelle, Paris; MSNG - Museo Civico di Storia Naturale, Genoa, Italy; MZUSP - Museu de Zoologia, Universidade de Sao Paulo, Sao Paulo, Brazil; RU - Rhodes University, Grahamstown, South Africa; SIO - Scripps Institution of Oceanography; SU - Stan- ford University, also listed as SNHM for Stanford Natural History Museum, specimens now de- posited at the CAS; TABL- Southeast Fisheries Center, Miami, Florida; UCLA - Fish Collection, Department of Zoology, University of California at Los Angeles; UMML- Rosenstiel School of Marine and Atmospheric Science of the Univer- sity of Miami; USNM - National Museum of Nat- ural History, Smithsonian Institution, Washing- ton, D.C.; ZMA- Zodlogisch Museum Amster- dam.
Material Examined
Listed below is the material utilized for osteo- logical examination in this study. The specimens are grouped by tribes and listed alphabetically within each tribe. Following each specific name is the museum abbreviation, museum catalogue number, number of specimens, range of the total length(s) of the specimen(s) involved. Abbrevia- tions are: CS, stained and cleared by the Taylor (1967) trypsin technique; GA, gill arches re- moved, stained and cleared; H, hyoid removed; S, skull preparation; X, radiograph. Specimens utilized only for vertebral counts are not in- cluded in this listing.
Ophichthidae - Benthenchelyini. Benthenchelys cartieri, DANA 3735, 2(105-115mm), CS.
Ophichthidae - Myrophini. Ahlia egmontis, SIO 67-87, 1(268), S; SIO 71-266, 1(337), CS. Muraen- ichthys chilensis, SIO 65-645, paratype, 1(248), CS; SIO 65-655, paratype, 1(276), CS, 1(292), S. Muraenichthys gymnopterus, SIO 69-276, 1(129), S, 1(144), CS. Muraenichthys gymnotus, SIO 69- 266, 1(244), CS. Muraenichthys macropterus, SIO 69-277, 1(181), CS. Myrophis plumbeus, SIO 69-
15
371, 1(182), CS. Myrophis uropterus, CAS 13971, 1(159), CS; BPBM 27209, 1(182), CS. Myrophis vafer, SIO 68-242, 1(193), CS, 2(265-325), S. Pseu- domyrophis micropinna, SIO 60-72, 1, head and trunk only, CS. Pseudomyrophis nimius, ANSP 110150, 1(350), CS. Schismorhynchus labialis, CAS 24687, 5(114-137), CS. Schultzidia johnstonensis, SIO 69-267, 1(138), CS.
Ophichthidae - Callechelyini. Aprognathodon platyventris, SIO 68-393, paratypes, 2(312-330), CS. Callechelys bilinearis, SIO 70-376, 1(260-+), CS. Callechelys cliffi, SIO 61-247, 1(218), GA, H, X; SIO 65-281, 1(298), GA, H, X. Callechelys eris- tigmus, SIO 65-185, paratype, 1(552), GA, H, X; SIO 65-354, paratype, 1(431), CS. Callechelys gal- apagensis, UCLA 64-40, paratype, 1(767), GA, H, X. Callechelys holochromus (holotype of Crypto- pterygium holochroma), USNM 154994, 1(801), X. Callechelys luteus, SIO 68-497, 1(1038), H, X. Callechelys marmoratus, SIO 69-269, 1(286), CS, 1(340), S. Callechelys melanotaenius, SIO 69-269, 1(401), CS. Callechelys muraena, TABL Oregon 2819, 1(235), GA, H, X. Callechelys nebulosus, SIO 71-197, 1(283), CS. Callechelys springeri (hol- otype of Gordiichthys springeri), USNM 121604, 1(372), X. Callechelys striatus SIO 71-165, 1(430), H, X. Letharchus velifer, holotype, USNM 31458, 1(396), X. Letharchus rosenblatti, SIO 67-40, para- type, 1(248), CS. Leuropharus lasiops, holotype, SU 57313, 1(174), GA, X. Paraletharchus opercul- aris, UCLA 64-38, 1(435), GA, X. Paraletharchus pacificus, SIO 65-321, 2(276-369), CS.
Ophichthidae - Bascanichthyini. Allips concol- or, holotype, CAS 13967, 1(375), GA, X. Bascan- ichthys panamensis, SIO 71-98, 1(425), CS; SIO 71-224, 1(295), CS, 1(510), S. Caralophia loxochila, SIO 70-228, 1(445), CS; SIO 70-376, 1(238), CS. Dalophis imberbis, SIO 72-290, 1(440), GA, X. Ethadophis byrnei, holotype, SIO 67-31, 1(508), GA, X. Ethadophis merenda, holotype, SIO 65-47, 1(530), GA, X. Leptenchelys vermiformis, holo- type, USNM 101785, 1(115), X. Phaenomonas cooperae, CAS 13964, 2(451-549), CS. Phaenom- onas pinnata SIO 65-348, 1(375), CS, 1(375), S.
Ophichthidae - Sphagebranchini. Apterichtus caecus, MSNG 41058, 1(435), X. Apterichtus flavi- caudus, SIO 69-364, 1(300), CS. Caecula ptery- gera, USNM 206375, 1(232), CS. Cirricaecula johnsoni, paratype, USNM 141189, 1(325), CS. Ichthyapus ophioneus, SIO 70-376, 1(337), GA, X. Ichthyapus selachops, SIO 61-232, 1(400), CS, 1(400), S; SIO 65-343, 1(234), CS. Ichthyapus vul- turis, holotype, ZMA 104.153, 1(240), X; SIO 69-
16
366, 1(446), GA, X. Lamnostoma kampeni, SU 24593, 1(435), GA, X. Lamnostoma orientalis, CAS 13959, 1(205), CS; CAS 13968, 1(229), CS. Stictor- hinus potamius, MZUSP 8959, paratype, 1(289), CS. Yirrkala kaupi, SU 26827, 1(345), GA, X. Yir- rkala lumbricoides, CAS 13969, 1(346), CS; para- type of Y. chaselingi, 1A 16190-601, 1(560), X. Yirrkala misolensis, CAS 13965, 1(335), CS. Yir- rkala tenuis, SIO 71-165, 1(370), CS. Yirrkala sp., BPBM 11858, 1(306), CS.
Ophichthidae - Ophichthini. Aplatophis chau- liodus, UMML 27209, 1(165), CS. Brachysomophis sauropsis, SIO 69-267, 1(323), CS; SIO 69-271, 1(197), CS. Cirrhimuraena macgregori, SIO 68- 434, 2(291-317), CS. Cirrhimuraena taeniopterus, CAS 13962, 1(445), GA, H, X. Elapsopis cyclor- hinus, SIO 69-267, 1(268), CS, 1(475), GA. Eche- lus myrus, SIO 69-369, 1(449), dissected. Echelus pachyrhynchus, SIO 69-370, 1(355), CS. Echiophis sp., UMML 29144, 1(298), CS. Evips percinctus, holotype, CAS 13966, 1(125.5), GA, X. Leiuranus semicinctus, SIO 61-132, 1(195), CS; SIO 69-268, 1(243), CS; SIO 69-273, 1(344), S. Malvoliophis pinguis, |A 3646, 1(470), CS. Myrichthys colub- rinus, SIO 69-272, 1(345), CS. Myrichthys macu- losus, SIO 68-497, 1(390), CS; SIO 69-272, 1(310), CS. Myrichthys xystrurus, SIO 65-335, 1(420), S; SIO 65-354, 2(243-268), CS. Myrichthys sp., SIO 34-371, 1(386), CS. Ophichthus altipinnis, CAS 14647, 1(915), GA, X. Ophichthus cephalazona, SIO 69-279, 2(230-330), CS. Ophichthus erabo, CAS 13960, 1(480), GA, H, X. Ophichthus ophis, SU 51724, dissected. Ophichthus rutidoderma- toides, CAS 28727, 1(330), CS. Ophichthus tri- serialis, SIO 61-193, 1(230), CS; SIO 69-252, 1(800), S, prepared skeleton. Ophichthus zopho- chir, SIO 60-304, 1(217), CS; SIO 65-166, 1(310), S, 1(340), S. Ophisurus serpens, RU 76-78, 1(325), CS. Phyllophichthus xenodontus, SIO 69-273, 2(270-305), CS. Pisodonophis boro, SIO 69-281, 1(410), CS. Pisodonophis cancrivorus, SIO 69- 307, 1(345), CS. Pisodonophis cruentifer, MCZ 34529, 1(235), CS. Pisodonophis daspilotus, SIO 72-73, 1(251), CS. Pogonophis fossatus, SIO 61- 227, 2(232-249), CS. Quassiremus evionthas, UCLA 64-19, 1(283), GA, X. Quassiremus nothochir, SIO 65-334, 2(271-342), CS. Scytalichthys miurus, CAS 13970, 1(235), CS. Xyrias revulsus, holotype, SU 6476, 1(890), GA, X.
Comparative Material - Non-ophichthids. The following material was stained and cleared with two exceptions. These, Gymnothorax mordax and Muraenesox coniceps, were examined from pre- pared skeletons.
SERIES 4, V. 41, #1 McCOSKER — EELS
Anguillidae. Anguilla rostrata, SIO 69-254, 1(210).
Muraenidae. Anarchias galapagensis, SIO 65- 345, 1(130). Echidna nebulosa, SIO 59-8, 1(178). Enchelycore bayeri, CAS GVF 1957-18, 1(255). Gymnothorax castaneus, SIO 65-291, 1(140). Gymnothorax mordax, SIO skeletal collection, 1(ca. 1 meter). Gymnothorax panamensis, SIO 61- 239, 1(180). Gymnothorax schismatorhynchus, CAS GVF 1958-13, 1(265). Muraena lentiginosa, SIO 65-354, 1(165). Uropterygius necturus, SIO 65-302, 1(175).
Simenchelyidae. Simenchelys parasiticus, SIO 68-479, 1(295).
Derichthyidae. Derichthys serpentinus, SIO 60- 239, 1(140).
Serrivomeridae. Serrivomer sector, SIO 63-374, 1(305).
Nemichthyidae. Nemichthys scolopaceous, SIO 65-243, 1(440).
Heterenchelyidae. Pythonichthys asodes, para- type, UMML 23481, 1(290).
Muraenesocidae. Muraenesox coniceps, SIO skeletal collection, a large adult.
Moringuidae. Moringua ferruginea, SIO 68-531, 1(305).
Congridae. Ariosoma_ gilberti, SIO 62-709, 3(175-190). Conger cinereus, SIO 68-531, 1(210). Gorgasia punctata, SIO 62-270, 1(365). Taenio- conger sp., SIO 62-42, 1(235).
Xenocongridae. Chlopsis apterus, LACM 32555, 2(152-155). Kaupichthys hyoproroides, SIO 67-45, 2(150-190).
Statistical Methods
Comparisons of vertebral means and variances were made with a standard ‘t’” test. Two com- puter-programmed grouping techniques were used to compare inter- and intra-generic rela- tionships within the Callechelyini. These were modifications of a clustering technique, the weighted variable group method (WVGM)_ of Sokal and Michener (1958), and of a recurrent group analysis (REGROUP) devised by Fager (1957). Each will be discussed briefly, although the original sources should be referred to_ if further information is desired.
Wormuth’s (1971) modification of WVGM, used by him in ommastrephid squid taxonomy, was used to identify the interspecific relation- ships of 18 of the 21 species of the Callechelyini. Cluster analysis is a technique widely used by numerical taxonomists, wherein each species (or individual) is termed an operational taxonomic
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unit (OTU). The program, as described by Wor- muth (1971), operates in the following manner:
Initially a matrix of m characters by n OTU’s is set up and the values in each row are standardized using row means and variances. From the standardized matrix (mxn) a product moment correlation coefficient is calculated. This matrix expresses the rela- tionships between all possible pairs of OTU’s quantitatively. At this point a cluster- ing procedure is employed to extract a graphic representation of the information contained in the correlation matrix. Any pair of OTU’s which has a higher correlation with each other than either has for any other OTU is put together as a group. An average correlation coefficient is computed for each group and it is, thenceforth, treated as a single OTU. In the WVGM a variable num- ber of new groups are formed on each cycle. At the end of each cycle, correlation coeffi- cients are recomputed based on the previous matrix. On any single clustering cycle two alternatives are available. One permits only groups of two OTU’s to form prior to recom- putation of the correlation matrix if their incorporation lowers the overall group cor- relation value by less than a_ preselected amount. As the results of both alternatives over a number of trials were very similar, the latter option was selected for its shorter computation time. The levels at which groups are formed are plotted. The graphi- cal representation of the results is termed a phenogram.
Data and characteristics used in program WVGM for the Callechelyini are presented in tables 8 and 9.
Recurrent group analysis was devised by Fager (1957) to identify communities of species on the basis of their co-occurrence in samples (Fager and McGowan, 1963; Fager and Longhurst, 1968) and later modified for taxonomic purposes by Ebeling and Weed (1963) and by Fager (1969). For each species pair, the program calculates an index of affinity. Fager and McGowan (1963) state that this index does not follow the hyper- geometric distribution exactly, and have there- fore replaced it with the geometric means of the proportion of common characteristics, corrected for the number of characteristics recorded for the species, such that:
=u Be
l= J AxB where | = index of affinity, ) = number of com-
mon characteristics, A and B = total characteris- tics recorded for species A and species B, and
17
where B = A. All characteristics are equally weighted. From the matrix of species pairs which is generated the largest possible group of species is selected. A “breakpoint” is selected such that pairs of species in which | is greater than or equal to that point are considered to show af- finity. For example, the selection of 0.500 as a breakpoint would group species which share somewhat more than “half” their characteristics. In this study, breakpoints of 0.500 and 0.600 were utilized, the latter appearing to give more reasonable groups without involving excessive al- ternative and unnatural groups. Once selected, the largest group is removed and the procedure is continued until all possible groups are formed. Where two or more groups of equal size are pos- sible, the program selects the one for which the sum of species pairs’ affinity indices is largest. Intergroup relationship can be calculated using the sum of characteristics shared by members of each group as a fraction of the total possible connections (see fig. 44). Inter-group similarity is therefore directly related to this fraction.
It should be noted that the computer programs used are each affected by the amount of, and manner in which, data are presented. The sensi- tivity of each program increases with increased data input. REGROUP is particularly insensitive to continuous data (e.g., vertebral and branchio- stegal ray numbers, body proportions) and treats each data interval equally. WVGM, by contrast, takes account of continuous data in calculating a correlation coefficient, but is somewhat more insensitive to dichotomous and_ trichotomous data. The characteristics used in each program are identified in tables 8 and 9.
OSTEOLOGY AND FUNCTIONAL ANATOMY
In the following section the osteology of Oph- ichthus zophochir is described and illustrated in detail. The bone complexes are treated sepa- rately, each beginning with a description of the condition of O. zophochir and followed by a discussion of variations and_ specializations among other genera within the family. Also in- cluded in this section are discussions of the oto- liths and of the gas bladder and digestive tract conditions of certain ophichthids.
Ophichthus zophochir was selected as the spe- cies with which other ophichthids are compared because it possesses the majority of ophichthid anatomical characters in a rather generalized state. This is not meant to imply that O. zopho- chir is the most primitive ophichthid, but rather
18
that by being generalized, and not specialized by means of extreme anatomical reduction, it provides a framework for comparison and discus- sion.
Neurocranium
The neurocranium of O. zophochir is com- pletely ossified and well fused along the cranial sutures. The skull is stout, rather elongate, and truncate posteriorly. The neurocranium of an adult O. zophochir, like that of most anguilli- forms, is small in relation to the total length of the fish. It occupies 5.5 percent of the TL, yet the neurocrania of more elongate ophichthids, such as Phaenomonas cooperae, occupy as little as 1.3 percent. Various aspects of the neuro-
SERIES 4, V.41, #1 McCOSKER — EELS
cranium of O. zophochir are illustrated in figures 2 and 3. Described below are the elements com- posing the neurocranium. Premaxilloethmovomer. The premaxillae, eth- moid, and vomer are fused into a single com- plex (PEV) articulating posterodorsally with the frontal and posteroventrally with the parasphe- noid, and forming the anterior margin of the orbit. The anterior portion of the PEV, the pre- maxillae, has been shown to be separate from the vomer in other eels, including Anguilla an- guilla (Norman, 1926), Derichthys serpentinus (Beebe, 1935), and Coloconger scholesi (Chan, 1967), yet in ophichthids there are no distinct sutures separating the elements, and their precise limits can only be determined ontogenetically. The premaxillary portion is expanded in most
ke
: rhs
Figure 2. Neurocranium of Ophichthus zophochir, SIO 65-166. Upper, dorsal view; lower, left lateral view. Scale represents 1 mm. Stippled lines represent cephalic lateralis canals. Abbreviations are: BO, basioccipital; BS, basisphenoid; E, ethmoid portion of pre- maxilloethmovomer; EO, epiotic; EX, exoccipital; F, frontal; N, nasal; OR, orbit; PA, parietal; PAS, parasphenoid; POR, postorbitals; PRO, prootic; PT, pterotic; PTS, pterosphenoid; SO,
supraoccipital; SP, sphenotic; VO, vomer.
Figure 3. Neurocranium of Ophichthus zophochir, SIO 65-166. Upper, ventral view; lower, posterior view. Scale represents 1 mm. Abbreviations are as in Figure 2. Sagitta (SA)
is outlined by stippled line.
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Figure 4. Neurocranium of Benthenchelys cartieri, DANA Sta. 3735. Scale represents 1 mm.
Figure 5. Neurocranium of Myrophis vafer, SIO 68-242. Scale represents 1 mm. Figure 6. Neurocranium of Muraenichthys chilensis, SIO 65-655. Scale represents 1 mm.
Figure 7. Neurocranium of Callechelys marmoratus, SIO 69-629. Scale represents 1 mm.
a9
SERIES 4, V.41,#1 McCOSKER — EELS
Figure 8. Neurocranium of Ichthyapus selachops, SIO 65-232. Scale represents 1 mm. Abbreviations are: BS, basisphenoid; OR, orbit.
Figure 9. Neurocranium of Stictorhinus potamius, MZUSP 8959. Scale represents 1 mm. Abbreviations are: BS, basisphenoid; OR, orbit.
Figure 10. Neurocranium of Bascanichthys panamensis, SIO 71-224. Scale represents 1mm.
Figure 11. Neurocranium of Myrichthys xystrurus, SIO 65-335. Scale represents 1 mm. Abbreviation PTS is for pterosphenoid.
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ophichthids (extremely so in Benthenchelys, fig. 4) and is toothed in all genera except Aprognath- odon. It narrows posteriorly to become the vomer, which is toothed in most ophichthids (exceptions are Schultzidia, Phyllophichthus, Leiuranus, and Leuropharus). The premaxillary and ethmoid dentition, here termed intermaxil- lary, is continuous with that of the vomer in O. zophochir. A gap separates the intermaxillary and vomerine dentition of many ophichthid genera, and appears to be a useful character to indicate relationship (table 1). The vomerine dentition does not continue onto the parasphenoid. The ethmoid portion forms the anterior margin of the orbit and the medial margin of the nasals. The ethmoid is perforated anterolaterally by the lat- eral commissure of the first cranial nerve.
Nasals. The nasals of O. zophochir are paired, thin, laminar, and cartilaginous along their ex- ternal edges. The anterior portion of the supra- orbital cephalic lateralis nerve tract passes through the canal along the median edge of the nasal. The nasals of the Myrophinae are either cartilaginous or absent. Nasal development among the Ophichthinae is variable. In certain long-jawed ophichthines (including Brachysomo- phis, Scytalichthys, and Aplatophis) the nasals are either rudimentary or absent. Nasal cartilage ex- tends from the anterior edge of the PEV; its de- velopment is quite variable, generally consisting of two short lateral rods; in certain genera it is fused centrally.
Parasphenoid. The parasphenoid (PAS) is a long, narrow, toothless bone, anteriorly overlying the vomer and forming the ventral margin of orbit. Centrally, it is spread laterally to form the anterior floor of the cranium, narrows posteri- orly, and splits into two short prongs. It forms the ventral margin of the orbit, and borders the orbitosphenoid, pterosphenoid, prootic, and basioccipital.
Prootic. The paired prootics (PRO) combine with the paired basioccipitals and pterotics to form the otic bulla. They are small, nearly rec- tangular, and highly perforated with numerous Openings for the passage of nerves and blood vessels. Through the most conspicuous foramen passes the hyomandibular trunk of the facial nerve (VII). Smaller foramina exist for the pas- sage of the orbital artery and the jugular vein. The major axis of the PRO is horizontal. The PRO are bordered by the parasphenoid medially, the pterosphenoid anteriorly, the sphenotic an- terolaterally, the pterotic dorsolaterally, and the basioccipital posteriorly.
2il
Basioccipital. The median basioccipital (BO) is a small, irregularly shaped bone which forms the posterior portion of the otic bulla. Its major axis, in contrast to the prootics, is vertical. It is bordered medially by the parasphenoid, anteri- orly by the prootics, and dorsally by the pterotics and exoccipitals.
Pterotic. The paired pterotics (PT) are elongate, narrow anteriorly, and broadly flared laterally and posteriorly, forming the lateral edge of the roof of the cranium. The cephalic lateralis nerve tract passes through the PT and opens anteriorly in the frontal and posteriorly at the posterior PT margin. Anteromedially the PT are bordered by the frontal, followed medially by the parietals and epiotics, anterolaterally by the pterosphe- noid and sphenotic, ventrolaterally by the prootic and basioccipital, and posteriorly by the exoc- cipitals. Posterior to the sphenotics, the PT forms a sheet-like eave extending beyond the body of the cranium.
Exoccipital. The paired exoccipitals (EX) form the dorsal and lateral margins of the foramen magnum. They are sutured along their dorsal midline, and extend posterodorsally and laterally as a semicircular sleeve around the foramen magnum. Ventrally, they contact the basioccipi- tal, and dorsally the supraoccipital. The foramen of the tenth cranial nerve opens posteriorly along the ventral EX-BO border, with the ninth opening lateroventrally from a foramen slightly antero- lateral to that of the tenth.
Supraoccipital. The supraoccipital (SO) is single, small, square to subrectangular in shape, and lies along the posterodorsal cranial midline. In O. zophochir the narrow median crest of the SO extends posteriorly as a small point. The condi- tion is typical of many ophichthids, although in certain generic groups, particularly Callechelys and related genera, they are rounded along the posterior SO margin. The SO extends anteriorly beneath the parietals, and is bordered laterally by the epiotics, posteriorly by the exoccipitals, and anteriorly by the prootics in most genera. In Schultzidia the SO has surfaced and has sepa- rated the parietals, extending anteriorly to con- tact the frontal.
Epiotic. The epiotics (EO) are paired, thin, and subrectangular. In O. zophochir they are bor- dered anteriorly by the parietals, laterally by the pterotics, and medially by the supraoccipital. Posteriorly their major axis is changed from hori- zontal to vertical in forming the dorsolateral mar- gin of the posterior cranial face bordering the exoccipitals. The EO, like the supraoccipital and
the pterotics, forms a narrow sheet-like eave along their posterior margins.
Parietal. The paired, thin, subrectangular pari- etals (PA) overlay the posterior margin of the frontal. They are bordered anteriorly by the frontal, laterally by the pterotics, posterolaterally by the epiotics, posteriorly by the supraoccipital, and fused medially. In certain ophichthids which have a prominent supraoccipital crest the median ridge development begins along the parietal mid- line and gradually increases to its posterior pro- jection. Castle (1972: fig. 10) has erred in illus- trating the PA of Benthenchelys as contacting the sphenotic; in no ophichthid did | find this juncture.
Frontal. The frontal (F) is a single long element which, along with the epiotics and_parietals, forms the roof of the cranium. Ontogenetically, the frontal is presumably formed from the fusion of paried lateral elements, but in juveniles and adults there is no evident suture. In O. zophochir the F is ridged posteriorly along the dorsal mid- line. In Aplatophis this ridge is developed as a sharp crest. Several nerve tracts pass through the F, including the anterior tract of the cephalic lateralis nerve and the transverse frontal com- missure, which is unique to the Ophichthidae. The frontal is deeply split anteriorly by the in- sertion of the ethmoid portion of the PEV in some genera, and bordered anteroventrally by the orbit and orbitosphenoid, ventrolaterally by the parasphenoid, laterally by the pterotic, and posteriorly by the parietals. The dorsalmost post- orbital of certain species of Ophichthus, Echio- phis, and Brachysomophis is weakly sutured to the frontal at the level of the transverse com- missure.
Basisphenoid (orbitosphenoid of others). The basisphenoid (BS) is a small, unpaired median bone with two lateral wings which forms the posteroventral margin of the orbit. It is bordered dorsally by the frontal, posteriorly by the ptero- sphenoids, and ventrally is supported by the parasphenoid (a myodome is not present). The BS in certain genera with elongate and depressed neurocrania has become narrow and elongate, as can be seen in a comparison of Ophichthus (fig. 2), Ichthyapus (fig. 8), and Stictorhinus (fig. 9);
Robins (1971: 164-165) has noted that the use of the term “orbitosphenoid” in other eel studies (including Gosline, 1950, 1951, 1952; Regan, 1912; Robins and Robins, 1967; Trewavas, 1932; and others) actually pertained to the BS. Chaba- naud (1936) stated that the teleostean BS is not
SERIES 4, V.41, #1 McCOSKER — EELS
homologous with that of higher vertebrates and proposed the name ‘‘porpitual’” for that bone in teleosts. Springer (1968: 43-44) agreed with Chabanaud’s conclusions but conserved the name “basisphenoid’’ because of its widespread usage in ichthyology, an act with which | fully agree.
Pterosphenoid (=alisphenoid). The small paired pterosphenoids (PTS) form the anterodorsal roof of the cranium. In O. zophochir they are con- cave, turning evenly from a longitudinal axis (along the margin of the frontal) to a nearly transverse axis which abuts the anterior margin of the sphenotic. They are bordered anteriorly by the frontal, dorsally by the pterotics, pos- teriorly by the prootic and sphenotic, and medi- ally by the parasphenoid. The conspicuous fora- men along the PTS-pterotic border is the an- terior opening of the trigemino-facialis chamber.
Otoliths. Ophichthid otoliths, like those of most anguilliforms, are small, and hence have received little attention either on a descriptive or a comparative basis. Studies are limited to those of Frost (1926), which included illustrations of the sagittae of Myrus vulgaris (=Echelus myrus), Ophichthus gomesii, and Pisodonophis boro, and the photograph of the sagitta of Myrophis lepturus in Kotthaus (1968). The sagitta (largest of the three otolith pairs) of twelve ophichthid species were compared in this study. The asteris- cus and lapillus were too small to be of com- parative value. Ophichthid otoliths are ovate and biconvex, with a shallow sulcus on the medial surface. They are particularly distinctive in having a shallow ostial channel which opens anteriorly rather than turning dorsally and opening from the sulcus, as is typical of the Congridae (cf. Friz- zel and Lamber, 1962: fig. A; Frost, 1926: figs. 10-11, 15). The sagittae of Ophisurus and Oph- ichthus (fig. 12) possess a short anterior rostrum and are more elongate than those of Ethadophis and Myrophis, which are roughly circular. Sagit- tae of Myrichthys and Echiophis are intermediate in shape.
Dentition. Dentition has often been used as a principal character to define and differentiate ophichthid genera. The location and shape of teeth was found in this study to be an important indication of relationship. The dentition of O. zophochir represents the generalized ophichthid condition in being multiserial, conical, and on all tooth bearing bones (vomer, ethmoid, pre- maxilla, maxilla, and dentary). Considerable vari- ation exists within the family, including the elongate fanglike dentition of Aplatophis, the molariform or granular dentition of Myrichthys,
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Figure 12. Otoliths (medial face, left sagitta) of several ophichthid species. Anterior
end up. Sulcus outline inked in. Scale represents 2 mm.
A. Ophichthus triserialis
B. Ophichthus zophochir
C. Ophisurus serpens
D. Echiophis intertinctus
E. Ethadophis merenda (orientation uncertain)
> Be Ge ae
Myrichthys xystrurus Echelus pachyrhynchus Aplatophis chauliodus Myrophis vafer
i) W
SERIES 4, V. 41, #1 McCOSKER — EELS
-—H
Figure 13. Head skeleton of Ophichthus zophochir, SIO 60-304. Scale represents 1 mm. Refer to Figures 2-3 (neurocranium), 14 (suspensorium), 17 (hyoid), and 19 (pectoral girdle)
for names of bones.
Pisodonophis and certain species of Muraenich- thys, the minute, nearly villiform dentition of Schultzidia, and the smooth toothless vomer of Leiuranus, Leuropharus, Phyllophichthus and Schultzidia. Characteristics of the dentition of ophichthid genera are summarized in table 1.
Suspensorium and Jaws
The conditions of the dentition, suspensorium, and jaws are directly related to the feeding habits of the various genera. In ophichthids, differences in feeding habits (e.g., major differences in prey items and adaptations of the predators to the different habitats) are greater between the spe- cies of different genera than between congeners. These differences are well evidenced in the form of the suspensorium and jaws of various ophich- thids. The juxtaposition of the neurocranium, suspensorium and jaws, pectoral girdle and hyoid apparatus of O. zophochir is illustrated in figure 13.
All elements of the suspensorium and jaws are paired.
Hyomandibular. The hyomandibular (HYM)_ is stout and shaped like an inverted right triangle. The HYM of strong-jawed piscivorous genera is generally strongly ridged for the attachment of the massive adductor mandibularis muscle. The dorsal surface of the HYM abuts the sphenotic and pterotic. A small irregular condyle along the antero-dorsal margin of the HYM fits into a shal- low socket formed along the sphenotic-pterotic suture. The large process on the posterior HYM
margin adjoins the anterior process of the op- ercle. The ventral portion of the HYM contacts the quadrate.
Quadrate. The small, stout quadrate (Q) is tightly sutured to the HYM. The vertical ridge along the outer face of the HYM is continuous along the Q. Ventrally the Q bears a broad rounded con- cave process that contacts the articular bone of the mandible.
Articular. The wedge-shaped articular (AR) is narrowed anteriorly, and slides into a pocket within the dentary. A remnant of the corono- meckelian is present along the inner face of the AR of O. zophochir; its presence in other genera was not systematically determined. Posteriorly, a grooved socket in the AR meets the rounded socket of the quadrate.
Dentary. The dentary (D) is the toothed bone of the mandible, joined by the articular pos- teriorly and adjoining its opposite member at the symphysis by a cartilaginous connection.
Postorbitals. The three postorbitals (POR) of most ophichthids are separate, weak ossicles that surround the nerve tract connecting the supra- orbital and infraorbital pore tracts. The POR of O. zophochir however, are specialized by en- largement and fusion to form a continuous strut bracing the mandible and neurocranium. This specialization, also present in other species of Ophichthus and Echiophis, is extreme in Brachy- somophis (fig. 15).
The antorbital cartilaginous strut which Gos- line (1952) described for Echelus myrus was not
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Yat 4 flea Oh)
Wy T N
Figure 14. Suspensorium and jaws of Ophichthus zophochir, SIO 65-166. Scale repre- sents 5 mm. Abbreviations are: AR, articular; D, dentary; HYM, hyomandibular; IO, inter- opercle; MX, maxilla; OP, opercle; PG, pterygoid; PO, preopercle; POR, postorbitals; Q, quadrate; SOP, subopercle.
A. Outer face
B. Inner face
26
SERIES 4, V.41, #1 McCOSKER — EELS
Figure 15. Right postorbital series of Brachysomophis sauropsis. Scale represents 1 mm. Abbreviations are: E, eyeball; MX, maxilla; POR, dorsal-most postorbital; io, infraorbital
pore tract.
found in other ophichthids studied (see Remarks on Echelus). A similar cartilaginous strut has been observed in other eels however, including the dysommid Atractodenchelys phrix and in the Syn- aphorbranchidae (Robins and Robins, 1970: 307). They felt “it (probably) represents either the pre- frontal or lateral ethmoid or their fusion.”
Pterygoid (=palatopterygoid). Pterygoid (PG) development is variable within the family, al- though a clear pattern of relationship was not apparent. The PG is reduced to a narrow splint in most ophichthids. In O. zophochir it is thin, laminar, pointed anteriorly, and blunt posteriorly. It is held in place by the dermal layer and con- nective tissue, and contacts neither the quadrate nor the hyomandibular. The PG of all ophichthids tapers anteriorly, and often posteriorly, is largely cartilaginous in many species, and does not ap- pear to serve any distinct purpose. Ahlia is ex- ceptional in differing from the closely related species of Myrophis in the shape of its PG and in lacking vomerine teeth (fig. 30). A true pala- tine is not present in ophichthids, as shown by Robins and Robins (1971) in their discussion of the “palatopterygoid arcade.”
Maxilla. The maxilla (MX) of all ophichthids is toothed, elongate, and possesses an anterior dorsal process which articulates with the PEV. Posteriorly, the maxillae of O. zophochir are truncate and do not extend beyond the articular. The generalized ophichthid condition however,
is that of a toothless, elongate, ossified or cartil- aginous extension of the MX beyond and lateral to the articular. The location of maxillary articula- tion with the vomer is affected by the elongation of the snout and jaw, and is quite variable within the family. The condition is certain ophichthid genera is illustrated in figures 16 and 30.
In concluding this section on the neurocran- ium and suspensorium and jaws, certain com- ments are in order relating to their specializa- tions and functional anatomy. Typical of the pis- civorous adaptations of species of Ophichthus, Brachysomophis, Echiophis and related species are the strengthening provided by the cranial vault, the elongate pterotics, the broad junction of the hyomandibular along the neurocranium, and the bracing of the maxillae to the frontal by means of the fused postorbitals. An analagous condition exists in the muraenid genus Gymno- thorax, in which a postorbital strut strengthens the jaws and suspensorium (cf. Burton, 1956: fig. 6). Other ophichthid genera, particularly among the Myrophinae and elongate ophich- thines, are adapted to diets of minute inverte- brate prey, and have extremely reduced neuro- crania, suspensoria, jaws, and dentition.
Opercular Series
The opercular series of ophichthids, and of anguilliforms in general, is greatly reduced. This reduction is apparently related to the increase
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Figure 16. Maxillary-vomer apposition of several ophichthids. Benthenchelys cartieri enlarged 20 times, all others 9 times.
A. Myrichthys xystrurus D. Callechelys marmoratus
B. Ophichthus zophochir E. Muraenichthys chilensis
C. Phyllophichthus xenodontus F. Benthenchelys cartieri
28
in number and importance of the branchiostegal rays as supporting elements for the branchial cavity (Greenwood, et al., 1966). Gosline (1959) has correlated the reduction of the opercular series, posterior displacement of the gill arches and pectoral girdle, and the separation of the pectoral girdle from the neurocranium with the peculiar branchial pump and circulatory mechan- ism of anguilliforms. Opercular reduction and deossification of cartilage, and the increase in the number of branchiostegals of ophichthids appear to be greatest in the smaller myrophines and elongate bascanichthyins and sphagebranch- ins. Within the Ophichthidae, the condition of O. zophochir closely approximates the general- ized (primitive) state (fig. 14). The opercle (OP), the largest of the series, is posterior to the hyo- mandibular and above the subopercle (SOP), with its ventral margin lying lateral to the dorsal margin of the SOP. The interopercle (lO) over- lays the SOP and is below the OP. The pre- opercle (PO), smallest of the series, overlays the (1O) and contains the tract of the preoperculo- mandibular nerve. The SOP and IO are the least ossified of the series, although the distal margins of most members of the opercular series are car- tilaginous in most ophichthids.
Several specializations in each subfamily are useful indicators of phylogeny. For example, the SOP is produced posteriorly as a projection en- closing the ventral and posterior margins of the OP in species of Myrophis (fig. 33), Ahlia, Mur- aenichthys (Gosline, 1951a: fig. 3), Pseudomyro- phis, and Schismorhynchus. This SOP-OP morph- ology is typical of other eel families, including certain Congridae (Asano, 1962; Rosenblatt, 1967), Moringuidae (Trewavas, 1932; Smith and Castle, 1972), Xenocongridae (Gosline, 1950, 1951b; Robins and Robins, 1967), and Xenomy- stax atrarius (Peden, 1972). The opercular series of Callechelys and related genera is reduced and has a conspicuously fringed appearance along the margin. The opercular series of Stictorhinus, Apterichtus, Ichthyapus, and related genera are quite reduced, with elements absent in certain genera.
Hyoid Apparatus
The hyoid apparatus and the associated branch- iostegals provide fundamental characters which help to unify the subfamilies within the Ophich- thidae. In particular, the broad overlap along the ventral midline of the branchial basket is herein considered a major phylogenetic character of the
SERIES 4, V.41,#1 McCOSKER — EELS
family, not evidenced by homology or converg- ence in other eel families. The importance of this character, which later led to the combining of the Neenchelidae, Echelidae (in part), and the Ophichthidae, was recognized by Myers and Storey (1939), Gosline (1952), Bertin and Aram- bourg (1958), BOhlke (1960) and Nelson (1966b).
The general usage of the term ‘‘epihyal” in the ichthvological literature has been incorrect. As Goodrich (1930: 405-406) has pointed out, the true epihyal is homologous with the hyomandib- ular, and the element incorrectly termed the epihyal represents the posterior ossified element of the ceratohyal. | am in agreement with Good- rich’s conclusions, however in view of its wide- spread usage in ichthyology, | have herein used the term ‘‘epihyal’”’ to represent the posterior of the two ceratohyal elements, and the term ‘‘cera- tohyal” for the anterior element.
The following description of the hyoid appara- tus is based on that of O. zophochir (fig. 17A). The apparatus consists of the unpaired glossohyal (GH) and urohyal (UH), and paired upper hypo- hyals (HH), ceratohyals (CH), and epihyals (EH). The interhyal is absent. The outer posterodorsal margin of the EH is connected by cartilage to the inner face of the quadrate and provides sup- port for the branchial basket. The CH and EH are connected by a stout cartilaginous strut af- fording little flexibility along the arch; further strengthening is provided by the flanking spike- like posterior extension of the CH along the outer edge of the EH. The GH is grooved along the posterodorsal half and extends forward as a small cylindrical teat. The GH and paired upper HH are interconnected by a weak cartilaginous plate. The upper HH is fused along a broad and slightly flexible suture to the CH. A ventrolateral extension of the CH braces the HH. The UH, lying ventrad to the HH, GH and CH, is flattened anteriorly and has a short cartilaginous connec- nection from its anterior midpoint to the dorso- ventral margin of the GH. Posteriorly, the UH extends as a slender ossified spike surrounded by a membranous sheath and overlays the branchiostegal rays. All the branchiostegal rays are inserted on the external face of the arch, 6 on the CH, 1 on the cartilaginous interspace, and 19 on the EH. The inner 3 and outer 9 rays are closely grouped basally and the remainder are more widely spaced. Rays 6-16 are expanded slightly at their bases but filiform for the re- mainder of their length. The rays broadly overlap along the ventral midline in a characteristic man- ner. The distal 19 rays of the left EH and cartil-
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=
Figure 17. Hyoid arch and branchiostegals of Ophichthus zophochir, an ophichthine, and Muraenichthys chilensis, a myrophine. Dorsal view. Scale represents 1 mm. Abbrevia- tions are: BR, branchiostegal rays; CH, ceratohyal; EH, epihyal; GH, glossohyal; HH, hypo- hyal; UH, urohyal.
A. Ophichthus zophochir
B. Muraenichthys chilensis (posterior-most branchiostegals not illustrated)
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aginous interspace are overlain by all the rays of the right arch, which are in turn overlain by the remaining left CH rays. This pattern of the left CH rays overlaying the right CH and EH rays which overlap the left EH rays is consistent within the Ophichthidae.
The location and number of branchiostegal rays among the genera of ophichthids (table 2) and the proximity of the branchiostegal rays to the hyoid arch differs markedly in the ophichthid subfamilies. In the Myrophinae, which appear to follow the generalized anguilliform condition, the branchiostegal rays are attached to the outer face of the EH, often with a single ray on the CH (fig. 17B, Muraenichthys). The remainder of the branchiostegal rays, which will hereafter be referred to as the ‘accessory branchiostegal rays’, are unattached and basally lie well behind the hyoid arch. In the Myrophinae, these vary from as many as 13 pairs in Benthenchelys cartieri to 42 pairs in Myrophis vafer. In the Ophichthinae, all branchiostegal rays are at- tached to the outer face of the hyoid arch( fig. 17A, Ophichthus), although in some species the rays have secondarily become detached.
The extreme development of this branchio- stegal apparatus is obviously a means of strength- ening the gill basket. The manner in which sev- eral ophichthines, particularly Ophichthus, Echio- phis, Brachysomophis, and Aplatophis have all the rays attached to the face of the hyoid is probably related to a diet of struggling prey, in contrast to the myrophine condition of free rays and their diet of comparatively weak prey. The reduction of the opercular apparatus and the posterior displacement of the entire gill arch complex necessitates a supplementary skeletal framework to prevent the gill basket from col- lapsing during the normal burrowing activities of ophichthids. The posterior displacement of the gill arches among anguilliform families is extreme in the Ophichthidae and the Moringuidae (see Nelson, 1966a: fig. 58), both of which comprise predominantly sand and mud-burrowing forms.
The accessory branchiostegal apparatus of ophichthid and echelid eels was recognized by earlier workers, but Parr (1930) was the first to describe it and suggest its function. He created the term ‘“‘jugostegalia’’ for the accessory skele- ton of the gill cover in species of Myrophis. Be- cause of their number he did not consider the attached rays to be homologous with the bran- chiostegals. In that the accessory rays are un- differentiable from the branchiostegal rays, espe- cially in those ophichthine species in which all
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rays are attached to the hyoid, | prefer not to use Parr’s term, jugostegalia. Problems occur in the consideration of jugostegalia as a separate en- tity, even if one assumes them to be homologous with the branchiostegals. For example, in follow- ing Parr’s concept of jugostegalia as those rays which are free from the hyoid, McAllister (1968: 85) stated that “Myrichthys (has) 28 (branchio- stegal rays) plus 4 jugostegalia...Myrophis 5 plus 34-36 jugostegalia.”” McAllister’s (p. 80) re- tention of the term jugostegalia ‘‘for those sec- ondarily multiplied, overlapping and free bran- chiostegals found in certain anguilliforms” is in- adequate as seen in the above usage. | therefore propose that a more flexible terminology be ap- plied to those rays, and prefer the term “‘acces- sory branchiostegal rays’’.
The branchiostegal rays also reflect intragen- eric and intergeneric similarities through their basal thickening and secondary multiplication. The outermost rays of all myrophines and several ophichthines are proximally broadened (e.g., Muraenichthys, fig. 17B, and Neenchelys, Nelson, 1966b: fig. 2a). This condition is similar to the general anguilliform condition as displayed by congrids, muraenids, anguillids, and other apodal families. In other ophichthines, particularly Ophi- chthus, Aplatophis, Myrichthys, and Quassire- mus, the branchiostegals are filiform throughout. The basal splitting or secondary multiplication of the few inner and outermost rays is probably secondarily related to the number and spacing of the rays along the arch. For example, in species of Echiophis and Ophisurus the branchiostegals on the CH are paired, and are often fused at their bases. No trends were apparent in this con- dition within the Ophichthidae, hence it appears to be of limited value as a phylogenetic indi- cator.
The urohyal of most ophichthines is produced posteriorly as an ossified spike. The UH of all myrophines is limited to an ossified basal plate with cartilaginous posterior filaments. The few ophichthines that lack the ossified spike are clearly derived from the generalized condition typified by Ophichthus, rather than from the somewhat similar myrophine condition. A cur- sory survey of other eel families indicates that the ophichthine condition is primitive in relation to the more specialized myrophine condition.
A major subfamilial difference is also evi- denced in the ceratohyal. Without exception, the CH of the Ophichthinae is split into an elongate and pointed distal portion and a shorter, truncate medial portion which connects, by means of
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Figure 18. Gill arch skeleton of Ophichthus zophochir, SIO 65-166. Dorsal view. Gill arches have been cut along the dorsal midline and spread laterally; left upper and lower pharyngeal tooth plates are removed to show underlying bones. Stippling indicates cartilage. Scale represents 1 mm. Abbreviations are: By, first basibranchial; Ci, first ceratobranchial; Ei, first epibranchial; H:, first hypobranchial; I2, second infrapharyngobranchial; LP, lower pharyngeal tooth plate; UPs, upper pharyngeal tooth plate.
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cartilage, with the EH (fig. 17A). The myrophine CH is not split, but is rather a simple bowed bone, distal to, and terminating at about the midpoint, of the EH. The myrophine condition appears to involve a unique reduction, whereas the ophichthine condition is similar to that of the Congridae (Asano, 1962; D. Smith, 1971; Rosenblatt, 1967) and other eel families.
The hypohyals of most ophichthines are like those of O. zophochir. In certain otherwise dis- similar genera, including Schismorhynchus, Apro- gnathodon, and Phyllophichthus, the HH are absent. Careful examination of the anterior end of the CH did not reveal a suture or line of fu- sion, so it might be assumed that the HH are lost altogether. Observation of an ontogenetic series might provide proof of fusion or absence.
Gill Arches
Certain elements of the anguilliform gill arch skeleton have been shown to be important in- dicators of phylogeny (Nelson, 1966a). The Ophichthidae differ from all other eel families in a combination of gill arch characters, includ- ing: a cartilaginous connection between the proximal ends of the dorsal part of the first and second gill arches (according to Nelson, peculiar to the Ophichthidae); first basibranchial either ossified or absent, all others cartilaginous, rudi- mentary, or absent; hypobranchials 1-2 ossified; second infrapharyngobranchial (ls) ossified. If one considers the anguillid or congrid gill arch conditions, that of numerous ossified elements with minor loss or reduction, to be primitive among the anguilliforms, then the ophichthids are considerably advanced in having several os- seus elements replaced with cartilage, and in having others reduced or entirely lost. Extending this supposition within the Ophichthidae, the Ophichthinae, and in particular the Ophichthini, are more primitive than the Myrophinae, which have lost the fifth ceratobranchial (C;) and have reduced or lost certain basibranchials (tables 3-4). The ophichthids are also specialized in having the gill arch skeleton displaced posteriorly in re- lation to the cranium. Among shallow-water eel families this condition is exceeded only in the Moringuidae (see Nelson, 1966a: fig. 58). Refer- ences to gill arches of ophichthid species are limited to Popta’s (1904) pioneering study of apodal gill arches (which treated Muraenichthys gymnopterus, Leiuranus semicinctus, Caecula polyophthalmus, Pisodonophis boro, and Myr- ichthys colubrinus), Nelson’s (1966a) detailed
SERIES 4, V.41, #1 McCOSKER — EELS
study, which included species from 18 ophich- thid genera, and Nelson’s (1966b) treatment of Neenchelys buitendijki.
The following description of the gill arch sys- tem of Ophichthus zophochir (fig. 18) illustrates the presumably primitive condition within the Ophichthidae. Terminology of gill arch elements follows that of Nelson (1969: 480). The _ basi- branchials are single elements, not intercon- nected, lying along the ventral midline; all other gill arch elements are paired. The first basibran- chial is ossified, slender, and connected by cartil- age to the first hypobranchials. Basibranchials 2-4 are cartilaginous and connected to the adjoining hypobranchial pair. Hypobranchials 1-2 are ossi- fied and stout. Hypobranchials 3-5 are cartilagi- nous, with 4 and 5 fused. Ceratobranchials 1-4 are ossified and subequal. Ceratobranchial 5 is reduced to a slender filament which is fused for most of its length with the ventral surface of the ventral pharyngeal tooth plate. Epibranchials 1-4 are short, stout, and bear various processes for cartilaginous or ligamentous attachment. The first infrapharyngobranchial (l:), as in all eels, is ab- sent. The second connects to the first epibranch- ial by a cartilaginous strap; this condition, as mentioned earlier, is peculiar to all ophichthids. The third is “T’’ shaped and distally supports the third upper pharyngeal tooth plate (UP3). The upper pharyngeal plates are separated by a su- ture, the third being much smaller than the fourth (UPs). Each plate bears along one margin a single row of slightly retrorse conical teeth which grades to a fine-toothed pavement. /n situ, the tooth plates overlie each other, and surround the esophageal canal so that the corresponding toothed areas of the upper and lower plates are aligned.
The third hypobranchial is cartilaginous in nearly all ophichthids. This specialization prob- ably functions to increase the flexibility of the gill arch skeleton and, in particular, to allow further anterior movement of the lower pharyn- geal tooth plates. For the same reason the fourth hypobranchial is never ossified. The species with ossified third hypobranchials, Dalophis imberbis, Aprognathodon platyventris, and Elapsopis cyclor- hinus, are highly specialized and not closely re- lated. Two examples of each of the latter two species were examined to rule out the possibility of anomalous specimens. Both specimens of Elapsopis had a well ossified Hs pair, and slender, nearly subequal tooth plates bearing conical biserial teeth. The two specimens of Aprognathodon were somewhat aberrant in the
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Hs condition. In one, the left Hz was well ossi- fied but the right was cartilaginous. The other had small discontinuous pieces of bone lying within a cartilaginous matrix on both sides. In both specimens the short, stout Hi-2 pairs nearly met along the ventral midline, and the small tooth plates bore several slender pointed teeth. In these exceptional species there has probably been a return to an ossified Hs condition rather than a retention of the primitive ancestral oph- ichthid condition, possibly related to a special- ized diet which would require less flexibility in the gill arch skeleton.
Microscopic examination and interpretation of the gill arch elements is often difficult, particu- larly in differentiating the rudimentary and cartil- aginous conditions of the basibranchials. Nelson (1966a: 393), for example, considered the fourth basibranchial condition of Leiuranus semicinctus and Machaerenchelys phoenixensis to differ, al- though most authors have regarded the latter species as a color variant synonymous with the former species. The interpretation of the UP3-UPs fusion also tends to be subjective and is not heavily relied upon. Since anomalies often occur in the gill arch skeleton, duplicate specimens were examined in this study when suspicious re- sults were encountered.
Nelson (1966a) identified certain ophichthid lineages on the basis of the gill arch conditions. These comprised (a) those genera with a moder- ately well-developed series of basibranchials and an ossified fifth ceratobranchial, (b) those with C; reduced or cartilaginous, and (c) those with very reduced basibranchials and lacking C;, i.e., the Myrophinae. Nelson erred in considering Echelus myrus to be an echeline (=myrophine) but did recognize the generalized condition of its basibranchials and C;. My study has shown Nelson correct in his other interpretations and now places other genera within his general framework.
The functional significance of the modification of the gill arches in apodal fishes was discussed by Nelson (1966a). The posterior displacement of the gill arches, the reduction and modification of osseus elements, and the absence of a firm interconnection with the cranium has_ trans- formed their function from prey catching (now left to the jaws and cranium alone) to one of moving large food items through a secondarily elongated pharynx. As Nelson (p. 404) has pointed out, ‘many of these same modifications have occurred independently among syngnathi- form fishes and symbranchiform fishes . . ., pos-
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sibly also as a result of spatial separation of jaws and gill arches.”
Pectoral Girdle
The pectoral girdle varies considerably within the Ophichthidae, grading from a well developed to a reduced condition in both subfamilies. The primitive condition, represented by Ophichthus (fig. 19A) in the Ophichthinae and by Myrophis in the Myrophinae (figs. 20E-F), includes the re- tention of the cleithrum (Cl), supracleithrum (SCI), scapula (=hypercoracoid) (Sc), and cora- coid (=hypocoracoid) (Co), and in the Ophich- thinae, the actinosts. The postemporal is absent and the pectoral girdle is not attached to the cranium in anguilliforms (Gosline, 1971). The pec- toral fin is best developed in genera such as Ophichthus, Echelus, Echiophis, Mystriophis, Ap- latophis, Malvoliophis, Cirrhimuraena, Pisodono- phis, and Pogonophis in the Ophichthinae, and Myrophis and Ahlia in the Myrophinae. The pec- toral fin rays are in some cases (Ahlia and Myro- phis) multiply-branched. Pectoral rays vary in number from three to four weak stubs in Bas- canichthys panamensis to 18 rays in Pogonophis fossatus.
The coracoid and scapula generally lie within a cartilaginous plate which provides a rigid sup- port for pectoral fin movement. When present, the pectoral fin base lies in a dorsoventral plane and is broad-based in relation to the fin length (extremely so in Myrichthys), offering little ro- tational movement. Observations of live Echio- phis sp. and Ophichthus triserialis indicate that those ophichthines use their pectoral fins to as- sist the body musculature in making short dart- ing movements during feeding. Observations of live Bascanichthys panamensis suggest that the highly reduced pectoral fin serves little, if any, locomotory function. In those forms lacking pec- toral fins, the cartilage, as well as the Co and Sc, is reduced or absent entirely. The trend in pec- toral girdle reduction is related to the burrow- ing habit of many ophichthids. The primary func- tion of the pectoral girdle as the structural sup- port for the pectoral fin has in burrowing forms become one of structural support for the poster- ior end of the branchial basket. In no species are all girdle elements absent, but in Cirricaecula (fig. 19N) and in species of Ichthyapus only the Cl remains, and in species of Muraenichthys the Cl is a thin curved bone which is nearly identical in appearance and in function to the last of the accessory branchiostegals. The SCI of several
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Figure 19.
\
SERIES 4, V.41, #1 McCOSKER — EELS
Pectoral girdle of various representative ophichthine genera. All are shown
in lateral view, right side, except Cirricaecula which is viewed ventrally. Abbreviations are:
Cl, cleithrum; Co, coracoid; PR, pectoral rays; Pt, pterygiophores; Sc, scapula; SCI, supra- cleithrum.
Sie G)) ott Ta SG) Sa)
. Ophichthus zophochir . Pisodonophis boro
. Elapsopis cyclorhinus . Myrichthys xystrurus
Quassiremus nothochir Aplatophis chauliodus
. Caralophia loxochila . Bascanichthys panamensis
Phaenomonas pinnata Caecula pterygera
. Lamnostoma orientalis
Callechelys marmoratus
. Aprognathodon platyventris . Cirricaecula johnsoni . Apterichtus flavicaudus
Yirrkala tenuis
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rc at
ID Wy,
Figure 20. Pectoral girdle of various representative myrophine genera. All are shown in lateral view, right side.
. Muraenichthys gymnopterus Muraenichthys chilensis . Benthenchelys cartieri . Ahlia egmontis Myrophis vafer Myrophis uropterus
_ Neenchelys buitendijki (from Nelson, 1966b: fig. 2c), pectoral fin rays not illustrated . Pseudomyrophis micropinna
ae (@) art (eal (o) (@Wesh
36
species of Muraenichthys is merely a thin sliver (e.g., M. chilensis, fig. 20B) and it is lost alto- gether in Schismorhynchus.
A peculiar Co and Sc condition exists in the Callechelyini and several of the Bascanichthyini, representing a unique ophichthid specialization which is not seen in other apodal fishes. It is nearly universal among eels for the Sc to be a nearly round bone (flattened slightly on the posterodorsal edge) lying above the Co (also nearly round but slightly flattened on the post- eroventral edge), one or both of which are fen- estrated. This is also the generalized ophichthine and myrophine condition. The Callechelyini possess either one or two small rod-shaped bones which are connected by cartilage and are oriented horizontally in the normal location of the Co (see Aprognathodon, fig. 19M and Cal- lechelys marmoratus, fig. 19L). Species of Phae- nomonas and Ethadophis, and the sphage- branchin Lamnostoma orientalis are similar in this condition. The homologies of these two rod- shaped bones are not entirely clear, but until further evidence is discovered, | will consider the anterior bone to be homologous with the Co and the posterior one to be homologous with the Sc. Pectoral girdle reduction in Myrich- thys provides an indictation of its generic homo- logies, particularly to species of Pisodonophis. The Sc in all species of Myrichthys is lost and the Co has lost its dorsal curvature (see fig. 19D). This condition is also that of Pisodonophis das- pilotus, a species clearly more similar to other Pisodonophis than to species of Myrichthys in other osteological characters. Further similarities in all species of both genera include the shape of the Cl and SCI. Other Pisodonophis examined have retained the Sc and a complete Co, a con- dition more like that of Ophichthus.
The ancestral condition of those genera which entirely lack the Co and Sc is not indicated by remnants of cartilage or bone or transitional species, and is therefore indeterminable. The loss of the Co and Sc in Ichthyapus, Apterich- tus, Cirricaecula and Quassiremus may have been independent, although the first three gen- era are related on the basis of other characters.
Lateralis System
The apodal lateralis system and associated bones have been shown to be useful indicators of relationship, particularly within the Congridae (Asano, 1962; D. Smith, 1972). Asano showed that the number of pores within the cephalic
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canal vary within and between genera of Japa- nese congrids. The lateralis system within the Ophichthidae was found to differ in a character- istic manner at the subfamilial and tribal level. It is best developed in the Ophichthinae and re- duced in the Myrophinae. The ophichthid later- alis system has been described and illustrated on several occasions, usually on a species by species basis and not in a comparative manner. These works include: Allis (1903), Ophisurus serpens and Echelus myrus (as Myrus vulgaris); Gosline (1951a), Ichthyapus vulturis (as Caecula_ platy- rhyncha); Hopkirk (1965), Ophichthus zopho- chir; Nelson (1966b), Neenchelys buitendijki; Blache (1968), Echelus myrus, E. pachyrhynchus and Myrophis plumbeus; Blache (1971), Mystrio- phis rostellatus, M. crosnieri, and Echiophis in- tertinctus; and Blache and Cadenat (1971), My- richthys pardalis, Bascanichthys spp., and Cal- lechelys spp.
The ophichthid lateralis system is divisible into seven canals: lateral line, supraorbital, infraorbi- tal, preoperculomandibular, temporal, supratem- poral commissure, and frontal commissure. The canals lie either within certain cephalic bones (frontal, pterotic, nasal, preopercle, postorbital, and dentary) or weakly ossified tubes (ossicles) which are broken at short intervals to provide flexibility. The Ophichthidae are distinctive in having the right and left sides of the cephalic lateralis system connected through the frontal and temporal canals.
The following description of the lateralis sys- tem of Ophichthus zophochir, a species which shows little reduction and minor specialization, illustrates the general ophichthine condition (fig. 21). The supraorbital canal connects with the infraorbital and temporal series posteriorly, and with its opposite member dorsally across the transverse frontal commissure. A single median supraorbital pore is present. Three supraorbital pores are associated with the nasal, the central pore lying within that bone. The anteriormost ethmoidal pore is connected to the supraorbital canal by a short cartilaginous connection. There are six infraorbital pores. Four lie horizontally beneath the eye in an ossified canal posterodis- tally overlying the maxilla, followed by two verti- cal pores lying behind the orbit and connected to a canal passing through the three postorbital bones. The supraorbital canal connects posteri- orly with the temporal canal and commissure, passing through the frontal and pterotics. A single median supratemporal pore is flanked lat- erally by a pore on each side. The temporal
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stp so
Figure 21. Cephalic lateralis system and associated bones of Ophichthus zophochir, SIO 60-309. Stippling indicates cartilaginous canal section. Scale represents 1 mm. Abbrevia- tions are: an, anterior nostril; es, ethmoid section of supraorbital pores; FC, transverse frontal commissure; io, infraorbital pores; LL’, anteriomost lateral line pore; N, nasal bone; pm, preoperculomandibular pores; pn, location of posterior nostril; PO, preopercle; por,
postorbital pores; POR, postorbital bones; so, supraorbital pore; stp, supratemporal pore. A. Right side view B. Dorsal view
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canal extends posteriorly to the lateral line canal and ventrally to the preoperculomandibular canal. The preopercular section connects by an ossified tube to the preopercle, with two ventrolateral pores passing from the bone. A cartilaginous connection with the third preopercular pore joins the preopercular and mandibular sections. By overlying the quadrate and angular-articular juncture this cartilaginous connection provides the flexibility necessary during jaw movement. The seven pores comprising the mandibular series are unevenly spaced along the dentary. The lateral line (LL) canal extends posteriorly from the preoperculomandibular-temporal canal juncture, loops above the branchial basket, and continues midlaterally to within 0.2 head length of the tail tip. There are approximately 150 LL pores, 51 of them before the anal origin. Lateral line ossicles are moderately ossified, separated at each pore, and open along the distal margin (fig. 22F). On the medial face of all LL ossicles there is a centrally located opening for the nerve. Lateral line ossicle development is reduced pos- teriorly and absent before the last few caudal pores.
Suprageneric relationships among ophichthid genera are indicated by repeating pore patterns in certain cephalic canals, particularly in the pre- opercular portion of the preoperculomandibular canal and in the temporal canal (table 5). The generalized ophichthine condition consists of three preopercular pores and a single temporal pore on either side of the median supratemporal pore (as in Ophichthus zophochir, Fig 21, and Ophisurus serpens, Fig. 24B). The third preoper- cular pore (pop*) is lost in certain Ophichthini and all Callechelyini and Bascanichthyini. Cer- tain Sphagebranchini are specialized in having a fourth preopercular pore (pop*) and a second temporal pore (tp’), as in Ichthyapus selachops (fig. 24A). This condition is not uniform through- out the Sphagebranchini, and may vary between and within populations, as evidenced by isolated populations of Ichthyapus vulturis (Randall and McCosker, 1975). The Myrophinae lack tp? and pop*. The pop® is present in Ahlia, Myrophis, Pseudomyrophis, Muraenichthys, and Schismo- rhynchus, but is absent in Neenchelys, Schultz- idia, and Benthenchelys (see Nelson, 1966a, figs. 21-25, in which Schismorhynchus was called Leptenchelys labialis, and Nelson, 1966b, fig. 1a).
The lateral line ossicles also indicate relation- ship in their degree of ossification, separation at each pore, and the pore position along the canal. Most pores lie below the midline of the
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LL canal, although some genera are specialized in having the pores located centrally within the canal. Lateral line ossicles are nearly solid struc- tures in the Sphagebranchini and Callechelyini, less substantial in the Ophichthini, and most re- duced in the Myrophinae (figs. 22-23).
Certain genera of the Ophichthini are special- ized in having a well-developed free sensory neuromast system along the sides and top of the head. The elaborate development of these sense organs has been generally overlooked. The neuromasts are not randomly scattered across the head region, but tend to follow distinct pat- terns. Nelson (1972) identified these lines of papillae in esocids as “‘pitlines’’, which are ap- parently homologous to the free sensory neuro- masts described herein. Following his terminol- ogy, the neuromast lines of Ophisurus serpens (fig. 24), beginning at the snout tip, include paired subnasal, antorbital, anterior, and cheek lines, and a single midline crossing the nape. Various degrees of development are also present in species of Ophichthus, Echelus, Pisodonophis, Quassiremus, Cirrhimuraena, Echiophis, Mystrio- phis, and Aplatophis. The neuromasts appear as minute papillae and are often difficult to discern due to skin rugosity and a waxy precipitate that forms on preserved specimens.
Neuromast development is probably related to the soft bottom habitat occupied by these spe- cies. Schwartz and Hasler (1966) suggested that LL pore development of the mudminnow Umbra limi is reduced and free neuromasts are devel- oped in response to its habit of digging into soft mud substrate. In doing so, they suggested, the pores of the LL canal could become impacted with mud and severly impaired. The numerous and widely distributed superficial organs, how- ever would remain functional. Rosenblatt and Rubinoff (1972: 362) inferred a similar adapta- tion in a heterenchelyid eel in noting that “the absence of lateral-line pores in P. asodes indicate that it may be a burrower in soft mud or in the semiliquid mud-water interface.” This inverse relation between sensory neuromasts and LL canal development is further evidenced by the ophichthids in that (a) a general correlation ex- ists between neuromast development and a mud, rather than a sand, substrate occupied by the species involved, (b) free neuromast development is absent in the Sphagebranchini where cephalic pore development is greatest, and (c) conversely, the mud-dwelling species of Echelus display ex- treme pore reduction and moderate neuromast development.
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me iii a
—
='
c a é a Paa65) SEC X Mer con SS (ESS Ese aie reenae | aly IE), ow 5 3 : Z D = r] = ASS = Fi noe . rac Os “A opens SE as ie E Figure 22.
3g)
nga @
4
son i —____—————“4
Fey ANTI i
e
\ (Rv Say go ————$———
L Q
AMWASOMegET BAI ee,
LIBERA WOR pgs —— s — ae.
NOU;
Lateral line ossicles of representative ophichthines. Distal view, right side
of mid-trunk region. Scales represent 1 mm. Stippling indicates lateral line canal.
. Aplatophis chauliodus
. Quassiremus nothochir
. Phyllophichthus xenodontus
. Aprognathodon platyventris Myrichthys xystrurus Ophichthus zophochir
. Cirrhimuraena taeniopterus
. Paraletharchus pacificus Callechelys eristigmus Pisodonophis cancrivorus
= 6 os) ol bal ) eyes oe
K. Phaenomonas pinnata Ethadophis byrnei
. Ichthyapus selachops
. Yirrkala tenuis
. Caralophia loxochila Bascanichthys panamensis
. Allips concolor Cirricaecula johnsoni Lamnostoma orientalis
iE M N O P. Q R. Se T. Elapsopis cyclorhinus
40 SERIES 4, V.41,#1 McCOSKER — EELS
_ — hi : =
TS OS TY eR a al era
© A ey eS eS Casas 2S eS ee a eee : : | a =] = ae = — <- US o = o.2 EOS OSSS oP PSS ee oe 50° Ss inched oe be Co ft eS eS Ea aS Sue rs 09s ed De ee ee a = 4 —— ——= Cc G
trey © Hs Ra
—
ee H
Figure 23. Lateral line ossicles of representative myrophines. Distal view, right side of
mid-trunk region. Scales indicate 1 mm. Stippling indicates lateral line canal.
A. Pseudomyrophis nimius E. Pseudomyrophis micropinna B. Myrophis vafer F. Ahlia egmontis
C. Benthenchelys cartieri G. Schismorhynchus labialis
D. Muraenichthys chilensis H. Schultzidia johnstonensis
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Figure 24. Cephalic pore and surface sensory papillae development in two ophichthids. Abbreviations are: an, anterior nostril; pop!, first preopercular pore; sp, surface sensory papillae (free neuromasts); stp, supratemporal pore; tp', first temporal pore.
A. Ichthyapus selachops, SIO 65-290. Dotted lines represent contours, not surface
sensory papillae.
B. Ophisurus serpens, unnumbered Rhodes University specimen, adapted from Allis
(1903), left lateral view. C. Ophisurus serpens, dorsal view.
41
42
Papillae also occur on the snout and tail tip of several ophichthids (cf. Rosenblatt and McCosker, 1970). Their function has neither been examined nor proposed, but might be inferred from ob- servations and analogous structures on other fishes. Tail tip papillae are generally small and may function as contact sensory devices in rela- tion to the tail-first digging behavior of most observed ophichthids. Certain of the snout pa- pillae are often larger (e.g., in Leuropharus lasi- ops and Evips percinctus) and may serve a gusta- tory as well as a contact sensory function. These papillae are best developed on snouts of several of the small-eyed permanent burrowing species (including species of Phaenomonas, Bascan- ichthys, and Ichthyapus). A gustatory function for similar papillae on the snout of a heterenchelid eel might also be inferred from Rosenblatt and Rubinoff’s (1972: 362) description of Python- ichthys asodes. They observed a reduction in the olfactory epithelium and the development of papillae on the jaws of this small-eyed species, and suggested this was related to a fossorial habit. Most species of ophichthids have not re- duced their olfactory epithelium, but probably encounter environmental problems similar to those faced by Pythonichthys in their modes of feeding.
Axial Skeleton
Regan (1912) considered the axial skeleton to be of major importance in separating eel famil- ies. He separated the Echelidae (considered by Regan to include Echelus, Ahlia, Myrophis, Par- amyrus, Chilorhinus, Muraenichthys, and Eomy- rust) and the Ophichthidae from the Congridae on the basis of the formers’ vestigial neural spines. He further separated the Echelidae from the Ophichthidae on the basis of the weaker ribs of the latter family. Gosline (1951a: 302-303) clarified Regan’s statements in his discussion of the ophichthid axial skeleton. Difficulties in the preparation and dissection of the anterior verte- brae have precluded their usage in this study in a systematically comparative manner.
The following description is based on the axial skeleton of Ophichthus zophochir (figs. 25-26). The first vertebral (V) centrum (CE) is reduced and not fused to the skull (fig. 25A). Its neural arch (NA) extends posteriorly over the second V. A lateral flange on the CE is present on the second and following trunk vertebrae. The NA of V 1-5 are smooth. Along the midline of the NA of V 1-12 is a single longitudinal crest which
SERIES 4, V.41,#1 McCOSKER — EELS
is split at its posterior margin to form two short ridges (fig. 26A). Neural spines (NS) are undevel- oped on the trunk vertebrae but become weakly developed points posterior to the 6th or 7th caudal vertebra. Epineurals (EN), epipleurals (EP), and pleural ribs (PL) extend posteriorly from the NA and parapophyses (P), and are approximately 5-7 V in length. The EN and EP of most ophich- thids begin at the posterior margin of the neuro- cranium. The P of V 1-12 are posteriorly directed and increase gradually in length. At approxi- mately V 13 the P are symmetrical and shaped like normal isosceles triangles. Foramina exist on each P, slightly posterior to mid-centrum (fig. 26B). The P of V 13-45 (approximate) are homogenous in size and shape; the lateral processes of the following 5-6 V are reduced. The first caudal ver- tebra (at which point the haemal arch begins to form) differs markedly in having its P split, the upper portion directed laterally to become the first caudal transverse process (CTP) and the lower directed downward to become the haemal arch (figs. 26C-D). The CTP are sharp lateral pro- jections, incised at their midlines to the centrum, and continuing nearly to the caudal tip. The haemal arch closure occurs at approximately the 10th caudal V. The closure however, is incom- plete, and consists of the joining of the posterior ends of the haemal spines. Intramuscular (IM) bones replace the neural and pleural ribs in the caudal region.
Differences in neural arch shape and sculptur- ing are evident in comparing the anteriormost five vertebrae of species of the type genus of each ophichthid tribe (fig. 25). The NA of V 1-5 of members of the Callechelyini can be distin- guished, at the tribal level, on that basis alone. Other characters from the axial skeleton were found to be useful indicators of relationship. The parapophyses of certain sphagebranchin genera, for example, were found to possess a marginal process which was lacking in related genera (fig. 33). Also, the CTP are lacking in most myrophins, yet in Muraenichthys and related genera the an- terior half of the column is similar to the ophich- thine column. Finally, the characteristics of the pleural ribs of Ahlia and Myrophis were found to differ from that of all other ophichthids in that they are limited to the anterior 15-20 vertebrae (see Remarks concerning Ahlia and Myrophis).
Vertebral numbers have been shown to be useful characters for the separation of species and populations of apodal fishes. Their applica- tion to the separation of genera is somewhat difficult because of the high degree of overlap
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Figure 25. Anteriormost five vertebrae of representative species from the tribes of ophichthids. All are shown in left lateral view. Scale represents 1 mm. Abbreviations are: Ce, centrum; EN, epineural; NA, neural arch; P, parapophysis; PL, pleural rib.
A. Ophichthus zophochir D. Callechelys marmoratus B. Stictorhinus potamius E. Myrophis vafer C. Bascanichthys panamensis F. Benthenchelys cartieri
44 SERIES 4, V. 41, #1 McCOSKER — EELS
CTP
Figure 26. Trunk and caudal vertebrae of Ophichthus zophochir. Arrows point anteri- orly. Abbreviations are: Ce, centrum; CTP, transverse processes of caudal vertebrae; EN, epineural; IM, intramuscular bone; NA, neural arch; NS, neural spine; P, parapophysis; PL, pleural rib. A. B.
Cc
Anterior view of 14th vertebra. Ribs appear foreshortened due to viewing aspect. Ventral view of 14th-16th vertebrae.
Dorsal view of last precaudal (51st) and anterior five caudal vertebrae (52nd-56th). Ribs and IM bones not illustrated.
Ventral view of vertebrae illustrated in C. Ribs and IM bones not illustrated.
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between genera, and a single mean value cannot be applied to a genus. Trends, however, are present within genera, and are probably relatable to the mode of life and associated anatomical specializations of the species involved. The spe- cies of Phaenomonas, Allips, and Bascanichthys, for example, tend to have increased vertebral numbers, primarily in the trunk region. An exam- ination of radiographs and gut contents of speci- mens of those genera disclosed the presence of copious sand and gravel particles in the gut and intestine, and the absence of any recognizable macroscopic animal material. On that basis as well as my observations of live specimens, | sug- gest that these eels indiscriminately eat their way through the substrate, digesting any utiliz- able organic material they encounter. In many ophichthids the length of the gut is increased by a loop that extends into the tail portion. The gut of species of Phaenomonas and Bascanichthys is straight, presumably to prevent blockage by sand particles passing through the lower tract. The in- creased trunk length, which is typical of these genera, perhaps reflects this problem, and may have been necessary to achieve this feeding mode. Certain callechelyins exhibit a similar in- crease in trunk vertebrae and a comparable life style.
Vertebral number is also the basis of correlat- ing the pelagic leptocephalus with the trans- formed adult stage of each eel species. Included in table 6 are the vertebral numbers of eel spe- cies examined and radiographed in the course of this study as well as several literature records which are assumed to be correct in species identification. The literature concerning numbers of eel vertebrae has not been exhaustively searched in that errors may inadvertently have been introduced through improper identification.
Caudal Skeleton
Differences in the myrophine and ophichthine caudal fins seemed important enough to most earlier authors to recognize the lineages as dis- tinct families. The Ophichthidae of nineteenth century authors was indeed a unique and unified assemblage; primarily due to the conspicuously pointed tail tip. Important members, most not- ably the species of Echelus, were erroneously ex- cluded from the Ophichthidae because they possessed a weakly developed caudal fin. Gos- line (1951a: 303) noted the similarity in the oph- ichthine and myrophine caudal skeletons, but felt that the continuous median fin condition
45
merited subfamilial separation. His findings, to my knowledge, have not been questioned by subsequent authors. He stated that:
osteologically, the difference between the tails of Muraenichthys and Cirrhimuraena is less than that between those of Cirrhimur- aena and Caecula platyrhyncha. Rudiment- ary rays are present around the tails of both Muraenichthys and Cirrhimuraena; they are embedded in flesh in Cirrhimuraena (as also in Myrichthys). In Caecula platyrhyncha, on the other hand, there are no rudimentary rays either around the tip of the tail or else- where. It is obvious from this discussion... that a separate family cannot be maintained for Muraenichthys on the basis of tail struc- ture.
The findings of this study are in agreement with Gosline’s. Difficulties in the dissection and prep- aration of the caudal skeleton has precluded its wide usage in this study. Careful examination of certain species however (including Echelus my- rus, E. pachyrhynchus, Leptenchelys vermiformis, and Bascanichthys tenuis), has clarified their position within the family.
The homologies of ossified elements within the apodal caudal skeleton are difficult to de- termine, and especially so in the case of the sharp-tailed ophichthins and sphagebranchins that have undergone major modification as an adaptation to rapid burrowing. The caudal tip of Ophichthus zophochir (fig. 27) is pointed, hard, and without visible caudal rays. The median fins submerge shortly (approximately one eye dia- meter) before the caudal tip. The underlying osteology is complex, as is illustrated in Figure 27. According to the terminology of Rosenblatt (1967), which was adapted from Nybelin (1963), there is but one weak centrum (CE). Fused to the CE is a pointed hypural (HY) and a much reduced neural arch (NA). Reduced caudal rays (CR) which lack basal elements are imbedded in the skin and weakly associated with the HY. The caudal skeleton of Myrophis vafer (fig. 28) differs somewhat from that of O. zophochir in possess- ing a short CE, two elongate HY, and a short cartilaginous extension posterior to each HY. The caudal rays of Myrophis are split anteriorly to receive the hypural plate. This is similar to the condition of caudal rays of xenocongrids (Robins and Robins, 1967), but appears to differ from the relatively unspecialized condition of Anguilla (Smith and Castle, 1972: fig. 19a). Blache’s illus- tration (1968: figs. 5, 10) of the caudal skeleton of Echelus indicates a caudal ray attachment sim- ilar to that of Myrophis. Present in most apodal
46 SERIES 4, V.41, #1 McCOSKER — EELS
Figure 27. Caudal skeleton of Ophichthus zophochir, SIO 65-166. Scale represents 1 mm. Abbreviations are: AR, anal ray; B, basal element of pterygiophore; CE, centrum; CR, caudal ray; DR, dorsal ray; HA, haemal arch; HY, hypural; IM, intramuscular bone; NA, neural arch; R, radial element of pterygiophore.
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Figure 28. Caudal skeleton of Myrophis vafer, SIO 68-242. Scale represents 1 mm. Ab- breviation CX is for cartilaginous extension of terminal vertebra.
47
48
caudal skeletons is a conspicous foramen be- neath the terminal centrum. It is well-developed in Myrophis, but reduced or absent in Ophich- thus and other ophichthines, resulting from the reduction of the lower HY. The haemal aches (HA) of the posterior caudal vertebrae of Ophich- thus and other ophichthines differs from that of Myrophis and other myrophines. The ophich- thine condition appears to be that of a simple rectangular lateral plate, whereas in the myro- phines a wide gap separates the HA into an an- terior and a posterior lateral flange.
The presence of a myrophin-like caudal fin in species of Echelus and Leptenchelys requires further explanation. As stated above, rudiment- ary fin rays are present in the sharp-tailed ophichthines. In the discussion of the evolution of the Ophichthidae it is hypothesized that the elongate bascanichthyins separated early in the evolution of the Ophichthinae, and in general, they possess a blunt rather than extremely sharp pointed tail tip. The tail of Bascanichthys tenuis is surrounded by a weak epidermis, which with- out careful inspection gives the appearance of a rayed caudal fin. The caudal tip of B. tenuis, when viewed with transmitted light, was found to lack caudal fin rays. The type and only known specimen of Leptenchelys vermiformis is similar to B. tenuis in possessing loose epidermis at the caudal tip, although minute fin rays appear to be present. The fin ray development in this juv- enile specimen may be anomalous, or may repre- sent a redevelopment of the rudimentary fin rays characteristic of the ancestral condition. The caudal fin of Echelus myrus, in contrast to the bascanichthyin fins, has well developed fin rays. The caudal skeletons of Ophichthus zophochir and £. myrus do not markedly differ other than in the development of fin rays. The produced rays appear to be a primitive retention of an ancestral condition, whereas the hard-pointed tail tip of other ophichthines was developed early in the evolution of the family. Other primi- tive morphological characters of Echelus that bear similarities to the generalized ophichthines and certain congrids would suggest that Echelus is a primitive ophichthid not far from the basal ophichthine stock.
The caudal skeletons of several ophichthids have been illustrated by earlier authors. Included are: Benthenchelys cartieri (Castle, 1972); Echelus myrus, E. pachyrhynchus, and Myrophis plumb- eus (Blache, 1968); Mystriophis rostellatus, M. crosnieri, and Echiophis intertinctus (Blache,
SERIES 4, V. 41, #1 McCOSKER — EELS
1971); Myrichthys pardalis, Bascanichthys spp., and Callechelys spp. (Blache and Cadenat, 1971); and Muraenichthys cookei and Cirrhimuraena macgregori (Gosline, 1951a).
Visceral Anatomy
The digestive tract and gas bladder have been shown by Asano (1962) to be useful taxonomic characters within the Congridae. This study is concerned primarily with osteology and the soft anatomy was therefore not examined in a sys- tematic manner.
A cursory examination of a myrophine, Myro- phis vafer (SIO 68-286, 240 mm TL), and an ophichthine, Ophichthus zophochir (SIO 65-166, 335 mm TL), disclosed very similar digestive tracts and gas bladder morphologies (fig. 29). The digestive tract in both species includes a gut diverticulum, or stomach (fide D. Smith, 1971), which branches off the anterior trunk region and extends posteriorly as a blind sac. The intestine, in both species examined, is a straight tube opening directly into the anus, whereas in other ophichthids it appears to extend partially into the caudal region and then to loop forward to the anus. The gas bladder (GB) connects anter- iorly to the intestine through the pneumatic duct (PD) at the mid-trunk level. The GB of both species is thin walled, surrounded by a thin mesentery, and lies alongside the intestine and dorsally within the peritoneal cavity. The GB is white, shiny and flexible; the digestive tract is pale in both species.
The gas bladder of the above-mentioned spe- cies occupies little of the peritoneal cavity, as might be expected from their fossorial habits. The GB of the pelagic species Benthenchelys car- tieri however, is considerably longer than that of either of the two fossorial species (Castle, 1972; fig. 25). Its length is approximately one- third of the trunk length, whereas the other two are approximately one-fourth to two-ninths. The GB of congrid eels is longer than the stomach (cf. Asano, 1962; D. Smith, 1971). The GB of the three ophichthids, by contrast, is consider- ably shorter than the stomach.
TAXONOMY
The following section includes an osteological definition of the family, a dichotomous key for the identification of genera, a diagnosis of the subfamilies and tribes, and an osteological and external morphological description of each genus of the Ophichthidae.
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49
Cc
Figure 29. Comparative anatomy of congrid and ophichthid digestive tract and gas bladder. The gas bladder has been separated from the intestine and the mesentery removed to improve clarity. The gas bladderx is stippled for identification, not to indicate pigmentation. Not drawn to scale. Abbreviations are: A, anus; E, esophagus; GB, gas bladder; H, heart; |,
intestine; PD, pneumatic duct; S$, stomach. A. Ophichthus zophochir, SIO 65-166
B. Benthenchelys cartieri, after Castle (1972) C. Conger myriaster, after Asano (1962)
The generic key is constructed using both osteological and external morphological char- acters. An attempt is made to group genera with- in the key in a natural manner to indicate rela- tionships.
In this section, redundancy is avoided wher- ever possible, however in several instances im- portant characters are repeated both in the tribal diagnoses and generic descriptions to facilitate comparisons. The generic descriptions are based, whenever possible, on the type species as well as the most morphologically divergent species within each genus, in an attempt to include the range of variation for each character examined. In a few instances the type species of the genus was unavailable for osteological study. Those genera are identified in the remarks section fol- lowing each description. The included nominal species of each genus are listed under the head-
ing “distribution”. Those species known to me only from literature records are indicated by an asterisk (*).
Abbreviations of several morphological char- acters and conditions are included for the sake of brevity. The reader is referred to the listing of abbreviations in the Materials and Methods of this paper. Also note that Body = Head + Trunk when used in body and tail length comparisons. The symbol = means ‘‘approximately equal to”.
Osteological Definition of the Ophichthidae From the present study the following osteo-
logical definition of the Ophichthidae may be developed:
(a) branchiostegal rays numerous and broad- ly overlapping along the ventral midline;
(b) supraorbital canals united by a trans- verse commissure through the fused frontals;
(c) temporal canal present;
(d) frontals of adults fused for their entire length and lacking an obvious suture;
(e) first epibranchial connected by a con- tinuous cartilaginous strap to the second infra- pharyngobranchial;
(f) no more than first basibranchial ossified;
(g) third hypobranchial usually cartilaginous;
(h) neural spines rudimentary or absent;
(i) tongue adnate;
(j) palatine absent;
(k) pterygoid well separated from vomer and generally free from hyomandibular.
Analytical Key to the Genera of Ophichthidae
la. Accessory branchiostegal rays originate be- hind ends of epihyal (EH), free rays more numerous than attached; caudal fin rays conspicuous, confluent with dorsal and anal, tail tip flexible; gill openings (GO) mid-lateral, a constricted opening .............. pe eee ey tee ae IMMWAROVOUIMUIMAG sacensee teat een
1b. All branchiostegal rays originate either in association with hyoid or before level of EH tips; free rays, when present, fewer than attached; tail tip a hard or fleshy fin- less point; GO mid-lateral to entirely ven- tral, un-constricted _...... Ophichthinae........ 9
2a.
2b.
3a.
3b.
4a.
4b.
SERIES 4, V.41,#1 McCOSKER — EELS
Neurocranium short, pointed anteriorly, broad posteriorly, length/depth = 3; eye large, ca. 6 times in head, orbital foramen large, its depth ca. 0.5 skull depth; an- terior nostril non-tubular; (posterior nostril before eye; pectoral fin moderately de- veloped) ........ Benthenchelyini .................... SRR er ee Oe, NAP ROR Benthenchelys Neurocranium more elongate, length/depth = 4; eye smaller, 10 or more in head, orbital foramen smaller, its depth much less than 0.5 skull depth; anterior nostril
TUMOUR cece cccssnccee My roonitiiip eens 3 Pleural ribs absent behind 15th-20th trunk vertebra; pectoral fin well developed ...... 4
Pleural ribs present on all trunk vertebrae; pectoral fin either absent or moderately developed)... eee 5 Vomerine teeth absent; dorsal fin origin (DFO) above or behind anus; maxilla stout, not tapering posteriorly, and abutting ptery- goid (fig. 30A); hypohyals (HH) absent, glossohyal (GH) rudimentary ............ Ahlia Vomerine teeth present; DFO anterior to mid-trunk region; maxilla thin and tapering posteriorly, not closely associated with pterygoid (fig. 30B); HH separated from
Figure 30. Vomer, maxillae, and pterygoid of Ahlia egmontis (A) and Myrophis vafer (B). Scale represents 1 mm. Abbreviations are: MX, maxillae; PG, pterygoid.
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5a.
5b.
6a.
6b.
ae
7b.
8a.
8b.
51
Figure 31.
ceratohyal by a gap, GH normally devel- oped Pectoral fin present, coracoid (Co) and sometimes scapula (Sc) present; posterior nostril lateral; transverse processes of Cau- Galieventebraen (GiiR)malbSemts see 6
Pectoral fin absent, girdle reduced to clei- thrum (Cl) and supracleithrum (SCI); pos- terior nostril labial; CTP present —.......... 7
Pectoral fin minute, Sc and actinosts ab- Sant 255s ee eeeaee Pseudomyrophis
Pectoral fin well-developed, Sc, Co, and AGCMIMOSUS PORESEMN sce Neenchelys
Teeth absent on vomer, absent or em- bedded on intermaxillary, those on max- illa and dentary minute or villiform; supra- occipital (SO) extends anteriorly to frontals, completely separating parietals; SO crest Al SC Il er ie NP RCE tc Schultzidia Teeth present on intermaxillary, maxilla, dentary, and vomer; SO not extending be- VONGmpanletalSaSOmcrest pnesenity asses 8
A prominent toothed groove on underside of snout, bordered by dermal folds, extend- ing anteriorly to anterior nostrils; hypohyals (HH) fused to ceratohyals (CH); suspen- sorium forwardly inclined ....................--------
Underside of snout without a prominent median toothed groove bordered by der- mal folds; HH broadly separated from CH by a suture; suspensorium nearly vertical Muraenichthys
9a.
9b.
10a.
10b.
Wile
11b.
12a.
2b:
Diagrammatic representation of a species with well developed head pores.
Neurocranium short, terete, length/depth ca. 3 or less; dorsal fin origin (DFO) on nape, above supraoccipital (SO); head pores reduced pop’, pop‘, and tp? absent (fig. 31); hyoid stout, thickened; (gill open- ings (GO) inferior, parallel or converging forward, isthmus narrower than GO length; pectoral fin absent) ...... Callechelyini -..... 10
Neurocranium longer, length/depth 4 or more; DFO, if present, behind nape; head pores generally not reduced, may include pop’, pop*, tp?; hyoid more slender ...... 14
Intermaxillary teeth absent; hypohyals (HH) absent; third hypobranchial (Hs3) ossified -. Aprognathodon
Intermaxillary teeth present; HH_ broadly separated from ceratohyal by a suture; Hs Cantilaeiim@ USa tere en ee oe eee lit
Anterior nostril rim not raised; dorsal fin origin (DFO) above epiotics; neurocranium slightly depressed, not convex across pari- etal-frontal region; four supraorbital pores; (anal fin absent; snout not grooved) ........ Letharchus
Anterior nostril tubular; DFO above supra-
occipital; neurocranium rounded across parietals and frontals; three supraorbital ONES) 7 at es veceen se tees eee eee ath one eae carareee 72 Anal fin absent; gill openings (GO) ex- panded ventrolaterally, forming broad DOGKEtS iis settee ee eee Paraletharchus Anal fin present; GO only slightly ex-
panded, not forming broad pockets ...... 433
ho
SERIES 4, V.41, #1 McCOSKER — EELS
Figure 32. Representation of underside of callechelyin snouts. A. Median groove pre- sent (13a in key), as in Callechelys. B. Median groove absent, as in Letharchus.
Figure 33. Diagrammatic representation of posterior trunk vertebrae (37th), ventral view. A. Parapophyses with anterior projection (16a in key), as in Apterichtus. B. Anterior projection absent (16b in key), as in Stictorhinus.
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13a.
13b.
14a.
14b.
15a.
15b:
16a.
16b.
lias
17b.
18a.
18b.
19a.
Vomer toothed; median groove on under- side of snout (fig. 32A); snout and nape not heavily papillate -...............-- Callechelys Vomerine shaft toothless; no median groove on underside of snout; snout and nape with numerous papillae ..Leuropharus Pectoral fin absent or vestigial; pectoral girdle reduced, consisting of a cleithrum (Cl), and may include a_ supracleithrum (SCI) and reduced scapula (Sc) and cora- coid (Co); median fins reduced or absent ok 8 2 ae ee ere eo 15 Pectoral fin present, generally well devel- oped; pectoral girdle consists of Cl, SCI (except in Scytalichthys), and generally Sc, Co, and actinosts; median fins generally elevated .............. @phirchithinieeee 29 Neurocranium depressed and_ elongate, length/depth = 4; head pores developed, tp? and pop® generally present; gill open- ings (GO) entirely ventral (except in Yir- nkalal\ ee Sphagebranchini Neurocranium deeper and shorter, length/ depth = 4; head pores reduced, tp*® and pop? absent; GO low lateral, crescentic -... Bascanichthyini All fins absent; parapophyses of posterior trunk vertebrae with an anterior marginal projection (fig. 33a); pectoral girdle re- duced to a cleithrum and a reduced or ab- sent supracleithrum; branchiostegal rays few, generally fewer than 20 pairs; second basiloranchiall(B>)) absent 22222 all Median fins present; anterior margin of posterior trunk vertebral parapophyses en- tire (fig. 33b); pectoral girdle includes cleithrum, supracleithrum, and reduced scapula and coracoid; branchiostegal rays more numerous, more than 20 pairs; Be CaltilalimOUse ee eet * 19 Upper pharyngeal tooth plates (UP; and UP.) fused; cirri present on upper lip ........ Cirricaecula
UP; and UPs separate; upper lip smooth.... oe eet irae ee OR a 18 Posterior nostril opening outside mouth, with a flap; anterior nostril tubular; eye moderately developed .............. Apterichtus Posterior nostril opening inside mouth, with or without a flap; anterior nostril flush with snout; eye minute .............. Ichthyapus Lateral head profile, from above, narrows sharply from epiotics to interorbital, then extends evenly to a pointed snout; body
19b.
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Daas
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Disa
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DE),
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stout, its depth less than 30 in its length; vomerine teeth enlarged, pointed and re- curved Lamnostoma Lateral head profile narrows evenly from epiotics to snout; body moderately elong- ate, its depth more than 40 in its length; vomerine teeth conical, not enlarged ....20 Eye minute, = 5 in snout; anterior nostril flush along snout; interopercle (IOP) absent 4 ens tns 5 Men, SC Re Sa er eae aE Stictorhinus Eye larger, = 3 in snout; anterior nostril tubular, or with a short but noticeable higmcal@© PRE TONES Citi ete oe ee 21 Neurocranium nearly flat across parietals and epiotics; gill openings (GO) with an anterolateral duplication forming a pouch; accessory branchiostegals loosely attached to hyoid, fewer than half associated with epihyal (EH); interopercle (IOP) subrec- tangular, margin entire -................. Caecula
Neurocranium raised along dorsal midline, not broad and flat across parietals and epiotics; gill membrane without a duplica- tion; accessory branchiostegals closely as- sociated with hyoid, more than half as- sociated with EH; IOP rounder, serrated along margin Yirrkala Tail short, .300-.360 of total length (TL); body extremely elongate, its depth ca. 75- NGO tina Syw linia eget eee ee eee eee 23 Tail longer, .395-.530 of TL; body not ex- tremely elongate, its depth usually less than. OWI ieee ee eee eee 24 Dorsal fin originating just behind occiput and ending less than 2 head lengths behind gillvopeningsssanall finmlackinigy: eee
Bee URE Seo RI shad Lean Aaa Phaenomonas Vertical fins low, but extending nearly to et atid pp ee oe oe « Hanet ke ge Gordiichthys Pectoral fin absent; supraoccipital crest
(SOC) extends from a parietal ridge, be- coming a raised point posteriorly _.......... 25
Pectoral fin a minute flap in upper gill opening corner; SOC nearly rounded, little OFMNOMDOStCHOR DO tee ees 28 Dorsal fin origin (DFO) behind gill open- ings (GO); tail longer than body; gill arches stout, third hypobranchial (Hs3) ossi- fied, fifth ceratobranchial (C;) a slender os- SifiedexhOch es ees eee ae et le Dalophis
DFO above or behind GO; body = tail; gill arches reduced, Hs cartilaginous, C; ab- sent
54
26a.
26b.
30b.
31a.
31b.
Bae
32b. 33a.
33b.
34a.
34b.
B5ar
Anterior nostril not tubular, its rim not raised, developed as an opening with lat- eral projections into it; underside of snout not grooved; intermaxillary teeth incon- SDLCUOQUSS ae. pee Fen ee Caralophia Anterior nostril tubular; underside of snout
grooved; intermaxillary teeth conspicuous Pt ted Eh ee re Ae 27 Median fins continuous around caudal, caudal fin rays evident ............ Leptenchelys Caudal tip blunt, finless -........... Ethadophis
Dorsal fin origin on head ....Bascanichthys Dorsal fin origin more than a head length
behindeuhiecadi asta aes Pee eA ey Allips Fifth ceratobranchial (Cs) absent ............ 30 Cs present as a slender rod, either ossified OT CantilasinOUs essa ee ee eee 34 Third preopercular pore (pop*) present;
pectoral fin rudimentary, smaller than eye; pectoral girdle reduced to cleithrum and SUpraclenthmnUinne ee ee Quassiremus pop® absent; pectoral fin well developed, longer than eye; scapula and coracoid of pectorallcirdlem present, —— 31 Hypohyals (HH) absent; maxilla with a for- ward projection, articulated ca. mid-vomer; supraoccipital (SO) rounded, lacking a pos- terior projection; urohyal (UH) deeply notched anteriorly; anterior nostrils with conspicuous leaflike appendages ................ Fie Bitte ad OG Soe Se Cree Phyllophichthus HH present, separated from ceratohyal by a suture; maxilla without anterior projec- tions, articulated before mid-vomer; SO with a posterior projection; UH not notch- ed beyond midpoint of basal plate; an- terior nostrils without leaflike appendages
Pnnenn ann es. Sones $F ONS ol | a AA ey 32 Jaws subequal; upper pharyngeal tooth plates (UP3-UP4) separate _........ Pogonophis Lower jaw inferior; UP3-UP4 fused ........ 33
Third hypobranchial (Hs) ossified; actinosts present; vomerine teeth present ..Flapsopis Hs cartilaginous; actinosts absent; vomer- ines absent, or 1-3 small teeth ....Leiuranus
Teeth molariform or granular; pectoral fin broad-based (fig. 34A)
Teeth pointed; pectoral fin base restricted, opposite upper half of gill openings (fig. AID) Wes: be 2 oes amd lee ee 36 Dorsal fin origin above or behind gill open- ings (GO); third preopercular pore (pop?) usually present; hypohyals (HH) narrowly separated from ceratohyal (CH); supraocci-
35b.
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SERIES 4, V.41,#1 McCOSKER — EELS
pital (SO) with a posterior projection ........ Soa ae see et Re ER Pisodonophis DFO well in advance of GO; pop® absent; HH broadly separated from CH; SO rounded, without a posterior projection... Ce ne el a atresia A cman eee Myrichthys Eye before middle of upper jaw, preorbital portion of neurocranium not extending be- yond posterior 2/3, rostral portion of eth- moid shorter than orbit; some teeth long and_ fanglike Eye over middle of upper jaw, preorbital portion of neurocranium extends nearly to or beyond middle of skull; rostral portion of ethmoid about equal in length to orbit; teeth inot aan elie eee ne 42 Lower jaw projects considerably; anterior teeth of both jaws long fanglike canines ex- tending far outside mouth; frontal crest a conspicuous sharp ridge ~.......... Aplatophis Lower jaw inferior or jaws nearly subequal; anterior teeth in jaws not fangs extending beyond snout tip; frontals not forming a sharp ridge, neurocranium rounded or flat dorsally Tail longer than body, compressed posteri- orly; pectoral developed, 5 or less in head length; third preopercular pore (pop’) pres-
QNiti «(fee ee 39 Tail shorter than or nearly equal to body; pectoral reduced, 7 or more in head leneth a pOp> absentee 40
Snout short, 7-12 in head length; second- ary cephalic papillae absent ........ Echiophis Snout longer, 6 or less in head length; secondary cephalic papillae well developed sh oe gee LY i a Mystriophis Postorbitals strongly developed, forming a postorbital strut; branchiostegals fewer than 20; postorbital region with a conspicuous transverse depression; lips fringed; colora- CON PAU ieee Brachysomophis
Postorbitals moderately developed, not forming a_ strut; branchiostegals 20 or more; dorsolateral profile of head even; lips entire; body spotted —...................... 41
Pectoral fin minute, more than 8 in head length; body much longer than tail ............ wine Es 9 reise Trad Freee te tS ae See Scytalichthys Pectoral fin better developed, ca. 7 in head length; body and tail nearly subequal -....... sik ct eRe ote fs Se Se EE in Xyrias Pectoral fin rudimentary, =~ eye; body longer than tail; (third preopercular pore
PROCEEDINGS CALIFORNIA ACADEMY OF SCIENCES
Figure 34. Diagrammatic representation of head and pectoral fin of two ophichthins. A. Pectorals broad-based (34a in key), as in Myrichthys. B. Pectoral base restricted (34b in key), as in Ophichthus.
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56
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44a.
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SERIES 4, V. 41, #1
McCOSKER — EELS
Figure 35. in key). Fl OSCE LG hehe aoe ee aw eat oe act Selene oe A IR a Evips Pectoral fin developed, noticeably longer than eye; tail longer than body ............ 43
Caudal fin present, confluent with dorsal and anal; temporal, postorbital, and inter- Ofbitallporeswalbsentsse ee Echelus
Tip of tail a finless point; temporal, post- orbital, and interorbital pores present ....44
Dorsal fin origin (DFO) before gill open- ings (GO); third preopercular pore (pop®) absent; upper pharyngeal tooth plates (UP3;- UP.) fused; pectoral girdle reduced, scap- ula (Sc), coracoid (Co), and actinosts ab- SC Mitac ete es! sad seks he Malvoliophis
DFO behind GO, or if before, the upper lip is fringed; pop’ usually present; UP3s- UP, separate; Sc, Co, and actinosts present So UTE ee eI OS ee en ea PE ee Eee 45
Snout very long, attenuate, ethmoid/neuro- cranium = .500; jaws slender and elongate, incapable of closing completely in adults .. Ophisurus
Snout moderate or short, ethmoid/neuro- cranium < .500 jaws not slender and elongate, capable of closing completely..46
Upper lip not fringed, although a barbel may be present; dorsal fin origin (DFO) behind gill openings (GO); opercular series stout, not weak and serrated along margin; aeons wistrlly S4) Ophichthus
Upper lip fringed (fig. 35); DFO generally on head, or above GO; opercular series weak, subopercle reduced; actinosts 1-2... Cirrhimuraena
Diagrammatic representation of an ophichthin with a fringed upper lip (46b
Kaup’s Genera
Kaup published his generic and specific de- scriptions twice in 1856. The earlier treatment, “Ubersicht der Aale’’ (1856a), is mentioned by John Edward Gray in the preface of the second, the Catalogue of Apodal fish in the Collection of the British Museum (1856b), published on 30 December 1856. Gray stated that ‘During the printing of the work and the engraving of the plates . . . a synopsis of the genera and new species has been published by Dr. Kaup, in Ger- man, in the Archiv. fur Naturgeschichte, xxii. 41, 1856." Kaup altered several generic names in the latter work (Echiophis became Echiopsis, Ophisurapus - Ophisuraphis, and Pisodonophis - Pisoodonophis), which has resulted in variant spellings of these generic names. Bleeker (1865) emended the spelling of several of Kaup’s gen- era, but Jordan (1919b) returned to Kaup’s earlier work. In the following listings of generic synony- mies, the pagination of Kaup’s later work (1856b) will follow that of the earlier, set off in paren- theses.
Type species were not designated by Kaup for his numerous and short-lived genera. Bleeker (1865), as first reviser, synonymized most of Kaup’s genera before types were designated. Jordan seems to have been the first to designate types for Kaup’s invalid genera, and it appears that in each case the first species listed by Kaup was regarded as the type species (cf. Jordan, 119 22))r
Subfamilial and Tribal Diagnoses and Generic Descriptions
PROCEEDINGS CALIFORNIA ACADEMY OF SCIENCES
Subfamily Myrophinae
DIAGNOSIS: GO mid-lateral, a constricted open- ing; DFO behind mid-trunk; caudal fin rays not reduced, externally visible, confluent with dor- sal and anal, tail tip flexible; nasals cartilaginous or absent; ceratohyal not divided into a short median and a long distal portion (fig. 17B); only basal plate of urohyal ossified, posterior exten- sion cartilaginous; accessory branchiostegal rays originate behind tips of epihyal, free rays more numerous than attached; branchial skeleton re- duced, basibranchials generally limited to first, fifth ceratobranchial absent; coloration uniform or darkened dorsally.
Tribe Benthenchelyini TYPE GENUS: Benthenchelys Fowler, 1934
DIAGNOSIS: Body moderately elongate, laterally compressed behind head; tail much longer than body; anterior nostril not tubular, posterior nos- tril lateral, before center of orbit; GO lateral, a horizontal ellipse; median fins elevated; pectoral fin moderately developed; head pores enlarged, a single preopercular pore, frontal commissure weakly developed; LL ossicles fragmentary, near- ly absent; neurocranium short, rounded (fig. 4); otic bulla, nasals, and SOC absent; maxilla broad, not produced posteriorly (fig. 16), articulating beneath anterior margin of orbit; gill arches weakly ossified, B: cartilaginous, Hs ossified, UP3;-UP, fused; pectoral girdle moderately de- veloped, SCI, Cl, Sc, and Co present; IM bones and ribs weakly developed, CTP absent; epi- pleurals limited to anterior 14-16 vertebrae; ver- tebrae distinctive (fig. 25), neural arches promi- nent; caudal more numerous than precaudal ver- tebrae; coloration uniform, slightly darker dor- sally. Other characters those of the single genus.
REMARKS: Benthenchelys cartieri was described by Fowler (1934) and referred to the Derichthy- idae (also Beebe, 1935). Gosline (1952) referred it to the Congridae. Subsequently, Castle (1972) has recognized it as an ophichthid after a thor- ough osteological study. The distinctness of this monotypic genus is herein felt to merit tribal recognition. The Benthenchelyini appear to be a distinctive offshoot from the generalized Myro- phini, specialized for a pelagic mode of life. Spe- cializations include the large eye, compressed body, enlarged median fins, enlarged head pores, and slender dentition. These characteristics con- verge with those of other pelagic eels, especially
57
the genus Derichthys. A myrophin relationship, particularly to the generalized Myrophis, is evi- denced in the hyoid and branchial arches, gill opening, frontal commissure, and disappearance of the epipleural ribs. The pelagic life style of Benthenchelys (and the associated eye enlarge- ment), unique to the Ophichthidae, could have evolved from the epipelagic breeding migrations of certain myrophines (see Cohen and Dean, 1970).
Benthenchelys Fowler
Benthenchelys Fowler 1934: 267. (Type species; B. cartieri Fowler 1934, by original designa- tion.)
DESCRIPTION (supplementing tribal diagnosis): snout blunt; jaws nearly subequal; eye large; an- terior nostril not tubular, a large anteriad open- ing; DFO slightly before vent; jaw and vomer- ine teeth conical, recurved, and uniserial, inter- maxillary teeth flattened and directed anteriorly, separated from those of vomer by a gap; nasal cartilage weakly developed; suspensorium an- teriorly inclined, jaw angle ca. 95°; maxilla broad, not produced posteriorly, articulating be- neath anterior margin of orbit; hyoid weak, GH elongate, HH separated from CH by a gap, UH a subrectangular plate anteriorly, a cartilaginous filament posteriorly; branchiostegal rays numer- ous, 8 along EH, the last 2 joined basally.
ETYMOLOGY: From the Greek 3 €2/90f(ben- thos), deep, and ‘Ev LEaus (enchelys; either masculine or feminine, here to be treated as masculine), eel.
DISTRIBUTION: A single pelagic species (100- 250 meters) over deep water in the central Indo- Pacific.
Tribe Myrophini TYPE GENUS: Myrophis Lutken, 1851
DIAGNOSIS: Body short to extremely elongate, laterally compressed behind head; tail generally longer than body; lower jaw included; anterior nostril tubular; posterior nostril either lateral or labial; GO lateral, a constricted opening; median fins low or elevated, DFO behind mid-trunk; pectoral fin present or absent; head pores vari- ably developed; LL canal weakly ossified; inter- maxillary dentition and vomerine, when present, continuous; neurocranium not raised along fron- tal or parietal midline, SO crest developed in
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some genera; orbit moderately developed; gill arches reduced, weakly ossified, Bi often absent, Bs.4 absent or rudimentary; pectoral girdle de- velopment variable; IM bones and ribs moder- ately to weakly developed, transverse processes of caudal vertebrae present in some genera; epi- pleurals limited to anterior trunk vertebrae in some genera; caudal vertebrae more numerous than precaudal; coloration uniform, often darker dorsally.
Ahlia Jordan and Davis
Ahlia Jordan and Davis 1891: 639. (Type species; Myrophis egmontis Jordan 1889, by original designation.)
DESCRIPTION: General characters those of My- rophis. Differences include: snout sub-conical, broad; DFO above or behind anus; vomerine teeth absent; maxilla broad, not tapering poster- iorly, closely abuts the short and broad pterygoid (fig. 30); HH absent, GH rudimentary; gill arches reduced, Hs and lz absent.
ETYMOLOGY: Named for Jonas Nicolas Ahl, au- thor of “De Muraena et Ophichtho”, with the noun suffix -ia (neuter).
DISTRIBUTION: A single Caribbean species.
REMARKS: The controversy regarding generic synonymy of Ahlia has never involved a detailed osteological study. Those considering it synony- mous with Myrophis (Parr, 1930: 8; Hildebrand, in Longley and Hildebrand, 1941: 17; Schultz and Woods, 1949: 171) did not consider the ab- sence of vomerine teeth to represent a generic character, but it was assumed by Jordan and Davis (1891: 639), Myers and Storey (1939: 158), and Wade (1946: 199) that this warranted sep- aration. Nelson (1966a: 398) considered Ahlia to be distinct on the basis of gill arch characters. The generic differences that | have identified are clearly related to feeding specialization in A. eg- montis, viz., tooth loss, maxillary-pterygoid brac- ing, and gill arch reduction, yet the universality of these characters among the species of Myro- phis suggests that the species of Myrophis form a natural group from which Ahlia is a specialized offshoot.
Cohen and Dean (1970) have recorded an in- teresting observation of offshore movements and a change in eye size accompanying the onset of sexual maturity in this species. Their observa- tions were made off Honduras, approximately 145 km from shore. | have made similar observa-
SERIES 4, V.41, #1 McCOSKER — EELS
tions within | km from land in the San Blas Archipelago, off the Atlantic coast of Panama.
Muraenichthys Bleeker
Muraenichthys Bleeker 1853b: 505. (Type spe- cies; M. gymnopterus Bleeker 1853, by original designation.)
Scolecenchelys Ogilby 1897: 246. Spelt Scolen- chelys by other authors. (Type species; Mur- aenichthys australis Macleay 1881, by original designation.)
Myropterura Ogilby 1897: 247. (Type species; Myropterura laticaudata Ogilby 1897, by origi- nal designation.)
?Aotea Phillipps 1926: 533. (Type species; Aotea acus Phillipps 1926, by monotypy.)
DESCRIPTION: Body short to moderately elong- ate, tail generally longer than body, laterally com- pressed posteriorly; snout sub-conical to blunt, not deeply grooved on underside; posterior nos- tril either along edge of lip beneath a flap or opening into mouth; DFO from mid-trunk to well behind anus; pectoral fin absent; pop® pres- ent; LL ossicles continuous, well developed for a myrophin; dentition variable, teeth often multi- serial, either conical or blunt, dentition of vomer continuous with that of intermaxillary; skull sub- truncate posteriorly; SOC present; maxilla elong- ate, slender posteriorly (fig. 16); suspensorium nearly vertical; opercular series weakly ossified, subopercle generally rudimentary, produced pos- teriorly in some species (as in Myrophis, fig. 36); otic bulla weakly developed; PG short, not brac- ing maxillae, reduced and slender in one sub- genus; HH separated from CH by a narrow gap; gill arches reduced, basibranchials absent, ls os- sified and UP;-UPs fusion variable; pectoral girdle reduced to a slender Cl and SCI; epipleural ribs on all precaudal vertebrae; CTP moderately developed.
ETYMOLOGY: From the Greek se UPA LU a an eel, and trots (ichthys; masculine), fish.
DISTRIBUTION: Nineteen recognized species from the tropical, subtropical, and warm temper- ate Indo-Pacific Ocean, including a single species from the eastern south Pacific. Material exists of undescribed Red Sea and western Pacific species.
REMARKS: Subgeneric lines within Muraenichthys were indicated by McCosker (1970) but were not designated pending a thorough osteological study. My examination and comparison of M.
PROCEEDINGS CALIFORNIA ACADEMY OF SCIENCES
gymnopterus, M. chilensis, and M. macropterus did not uncover osteological differences compar- able to those used to separate other closely re- lated ophichthid genera. This result was unex- pected in that the external morphology differs considerably within the genus, including differ- ences in snout form (from blunt to acute), in body depth (15-50 times in total length), in the number and position of head pores, in dentition, and in the character of the posterior nostril. Sub- generic lines may be identified in the following manner:
Posterior nostril opens on the outer lip as an elongate slit with an anterior flap; a single pore between the anterior and_ posterior nostrils; jaw teeth usually in bands, inter- maxillary teeth in a patch; UP3-UPs fused in species examined; snout usually blunt; body usually stout, its depth ca. 15-25 in TL ........ ee Subgenus Muraenichthys Bleeker
Posterior nostril opens into mouth, covered by an exterior valvular flap; two pores be- tween nostrils; jaw teeth uniserial or bi- serial, intermaxillary teeth not in a broad patch; UP3-UPs separate in species exam- ined; snout usually acute; body moderately elongate, its depth usually more than 25 in see ene. Subgenus Scolecenchelys Ogilby
The subgenus Muraenichthys includes M. gym- nopterus Bleeker (the type species), M. hattae Jordan and Snyder, M. schultzei Bleeker, and possibly M. macrostomus Bleeker, M. philippin- ensis Schultz and Woods, M. sibogae Weber and de Beaufort, and M. thompsoni Jordan and Rich- ardson. The subgenus Scolecenchelys includes M. australis Macleay* (the type species), M. chil- ensis McCosker, M. acutirostris Weber and de Beaufort, M. cookei Fowler, M. gymnotus Bleeker, M. macropterus Bleeker, M. breviceps Gunther, and possibly M. iredalei Whitley. Also included in Muraenichthys, but not here allocated to a subgenus, are Myropterura laticaudata Ogilby, Chilorhinus vermiformis Peters, Muraenichthys devisi Fowler, M. xorae Smith*, and M. godeffroyi Regan. My specimens of M. macropterus dis- agreed with Nelson’s (1966a) description in hav- ing an unfused UP3-UP4.
The genera Muraenichthys, Schultzidia, and Schismorhynchus display obvious similarities at- tributable to a common ancestry. Primitive and advanced conditions of certain characters may be identified among the approximately 24 species
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involved (many of the species included are known to me only from the literature and not from specimens). For example, postulated primi- tive conditions include the moderately elongate body, sub-conical snout, posterior nostril open- ing into the mouth, numerous head pores, uni- serial or biserial conical teeth, presence of the SO crest, posterior development of the sub- opercle, separate hypohyals, ossified second in- frapharyngobranchial, separate UP3-UPs, and con- spicuous cleithrum and supracleithrum. Species of the subgenus Scolecenchelys are clearly the most primitive, with the species of the subgenus Muraenichthys, and Schultzidia and Schismor- hynchus as specialized offshoots. The develop- ment of transverse processes on the caudal verte- brae, shared by these genera, is unique among the Myrophinae and without apparent antece- dents in more primitive genera such as Myrophis.
Aotea, type species A. acus, was described by Phillipps (1926) on the basis of a partially di- gested specimen from New Zealand waters, and placed in Muraenichthys by Castle (1967). Whit- ley (1968) placed A. acus in the synonymy of Muraenichthys breviceps Gunther, yet Phillipps (1926: 533-534) characterized A. acus as having “fins absent’ and ‘a hard folded portion be- neath body posterior to head apparently indi- cat(ing) gill-openings...”, both of which would exclude Aotea from the subfamily Myrophinae. Phillipps’ sketchy description of A. acus does not obviously agree with any known _ ophichthine genus, but best fits Apterichtus, Ichthyapus, and Cirricaecula. Further examination may discover that Aotea acus is a species of Apterichtus in that the species of the latter two genera are not known from even as far south as Australian waters.
Myrophis Lutken
Myrophis Lutken 1851: 14. (Type species; M. punctatus Lutken 1851, by monotypy.)
Paramyrus Gunther 1870: 51. (Type species; Conger cylindroideus Ranzani 1838, by Jordan and Davis (1891) as first revisers.)
Holopterura Cope 1871: 482. (Type species; H. plumbea Cope, 1871, by monotypy.)
Hesperomyrus Myers and Storey 1939: 157. (Type species: H. fryi Myers and Storey 1939 = My- rophis vafer Jordan and Gilbert, by original designation.)
DESCRIPTION: Body stout to moderately elong- ate, laterally compressed throughout; snout sub-
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conical to conical and moderately elongate; eye moderate; posterior nostril along edge of lip be- neath a flap or opening into mouth; DFO before mid-trunk region; pectoral fin moderately devel- oped, longer than eye; pop® present; teeth conical, uniserial or biserial in jaws and vomer; skull sub- truncate posteriorly (fig. 5); SOC present; maxilla elongate, slender posteriorly (fig. 30B); sub- opercle produced posteriorly as a posteroventral border to the opercle (fig. 36); otic bulla weakly developed; PG short, not bracing maxilla; Hs cartilaginous, UP3-UP, fused in one species; Cl and SCI slender, Sc, Co, and an actinost (2) well developed; epipleural ribs limited to anterior- most 15-20 vertebrae; CTP absent.
ETYMOLOGY: From the Greek Bu Pos, Myrus, and OPCS (ophis; masculine), snake.
DISTRIBUTION: A circumtropical genus of nine nominal species. Included are: Myrophis punc- tatus Lutken (WA), M. australis Castelnau (IP)*, M. cheni Weng (IP)*, M. lepturus Kotthaus (IP)*, M. platyrhynchus Breder (WA)*, M. vafer Jordan and Gilbert (EP), Conger uropterus Temminck and Schlegel (IP), C. cylindroideus Ranzani (EA)*, Holopterura plumbea Cope (EA). Incertae sedis: Myrophis frio Jordan and Davis (WA)*.
REMARKS: Schultz, et al. (1953: 68) erroneously included Parabathymyrus Kamohara in the syn- onymy of Myrophis. D. Smith (1971) recognized it as a valid congrid genus of the subfamily Ba- thymyrinae.
Figure 36. Opercular series of Myrophis vafer, SIO 68-242. Right side, distal view. Scale repre- sents 1 mm. Abbreviations are: IO, interopercle; OP, opercle; PO, preopercle; SOP, subopercle.
SERIES 4, V. 41, #1 McCOSKER — EELS
Castle (1963: 16) has discussed the identity of the congrid Gnathophis heterognathus (Bleeker) Which has been erroneously included in Myro- phis by recent authors.
Neenchelys Bamber
Neenchelys Bamber 1915: 479. (Type species; N. microtretus Bamber 1915, by monotypy.)
DESCRIPTION: Body moderately elongate, com- pressed posteriorly; body shorter than tail; snout sub-conical; eye moderate; posterior nostril an elongate slit before lower margin of orbit; DFO before mid-trunk; pectoral fin moderately de- veloped, longer than eye; pop*® absent; teeth conical, uniserial except at vomerines and inter- maxillary; skull rounded posteriorly; nasal condi- tion unknown; SOC absent; maxilla elongate and slender posteriorly; subopercle not developed posteriorly (fide Nelson 1966b, fig. le); otic bulla weakly developed; Bi rudimentary, lz ossified, UP;-UP, separate; pectoral girdle developed, SCI, Cl, Sc, Co, and an actinost (?) present; epipleu- ral rib condition unknown.
ETYMOLOGY: Presumably from the Greek W€z , new, and é UZLEDLS (enchelys; feminine or masculine, treated as masculine by Bamber), eel.
DISTRIBUTION: Two. species, N. microtretus Bamber* from the Red Sea, and N. buitendijki Weber and de Beaufort* from the Indian Ocean.
REMARKS: Specimens of Neenchelys were un- available for this study. The description is pre- pared from Nelson’s (1966b) osteological and Mohamed’s (1958) morphological description of N. buitendijki. Nelson (1967) noted the presence of overlapping branchiostegals in the holotype of N. microtretus (apparently the only known specimen) but did not compare it with N. buiten- dijki.
Nelson (1966b: 323), in commenting on Wade’s (1946) description of Pseudomyrophis micro- pinna, stated that ‘‘there is no character signifi- cant enough to maintain Pseudomyrophis as a genus distinct from Neenchelys. P. nimius, on the other hand, seems distinctive enough to be placed in a genus of its own.” My osteological examination of the species of Pseudomyrophis, which | have found to be congeneric, allows further comment on this relationship. The two genera show certain similarities in morphology and habitat (living in mud bottoms in moderately deep water) and are more closely related to each other than to other genera. Osteological simili- larities include the shapes of the neurocrania,
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pterygoids, maxillae, gill arches, hyoid arches, and caudal vertebrae. The characters used in the generic key to separate these genera may be ex- panded in the following manner:
DFO in anterior trunk region; snout conical; pectoral fin well developed, = snout; pop? absent; subopercle small, sub-rectangular; (pop? and subopercle condition of N. micro- ARERUISMUIMNIKTMOWWIMN)) 22---2020e-002s-c2e 2222-2 Neenchelys
DFO in posterior trunk region; snout broad, tumid; pectoral fin minute, = eye; pop? present; subopercle produced posteriorly along ventral and posterior margins of op- BCS SR ee Pseudomyrophis
Pseudomyrophis Wade
Pseudomyrophis Wade 1946: 199. (Type species; P. micropinna Wade 1946, by original designa- tion.)
DESCRIPTION: Body moderately to extremely elongate, laterally compressed throughout; snout broad, tumid; eye small to moderate; posterior nostril an elongate slit before lower margin of orbit; DFO behind mid-trunk; pectoral fin min- ute, smaller than eye; pop’ present; teeth coni- cal, uniserial throughout, except at anterior vo- mer and intermaxillary; skull rounded _ posteri- orly; nasals ossified along canal only, nasal car- tilage weakly developed; SOC absent; maxilla elongate, slender posteriorly; subopercle similar to Myrophis (Fig. 36), produced posteriorly as a slender posteroventral border to opercle; otic bulla weakly developed; PG short, not produced anteriorly; Bi and ls ossified, UP3-UP4 separate; pectoral girdle reduced to Cl and SCI (and frac- tional Co? in P. micropinna); epipleural ribs on all precaudal vertebrae.
Cha ETYMOLOGY: From the Greek W€EUPAYS (pseudes), false, -o-, and Myrophis (masculine), a genus of ophichthids.
DISTRIBUTION: Two New World species, P. ni- mius Bohlke (Caribbean) and P. micropinna Wade (eastern Pacific).
REMARKS: The species of Pseudomyrophis are strikingly different in body depth and head length, yet an osteological comparison did not uncover differences that are clearly generic. Other proportional differences are also related to the extreme elongation of P. nimius. The mean difference in vertebral number between species (ca. 50) is less than that between species
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of Phaenomonas (ca. 70). Both species are ap- parently adapted to soft mud bottoms in water relatively deep for ophichthids (P. micropinna from depths of 45-60 fms, P. nimius to 400 fms).
Schismorhynchus McCosker
Schismorhynchus McCosker 1970: 509. (Type species; Muraenichthys labialis Seale 1917, by original designation.)
DESCRIPTION: General characteristics those of Muraenichthys. Differences include: body mod- erately elongate; body shorter than tail; snout conical, elongate, with a prominent toothed groove on underside; anterior nostril an elong- ated tube as long as eye; posterior nostril opens into mouth; DFO in posterior trunk region; pop? and median interorbital pore absent; teeth coni- cal, uniserial; maxilla broad, not becoming slender posteriorly; subopercle produced posteri- orly as in Myrophis (fig. 36); suspensorium an- teriorly inclined; HH fused to CH (or absent?), GH rudimentary; gill arches extremely reduced, Bi, Hs, and lI» absent, UPs3-UPs fused, lower tooth plate elongate (see Nelson, 1966a: figs. 14-15); pectoral girdle reduced to a slender Cl.
ETYMOLOGY: From the Greek CLIT UN : : O 4 : (schisme), cleft, and 7 V zx Of — (latin- ized as rhynchus, masculine in accordance with item 30(a)(3) of the International Code of Zoo-
logical Nomenclature), nose.
DISTRIBUTION: A single species, widespread in the central and western Pacific ocean.
Schultzidia Gosline
Schultzidia Gosline 1951a: 309. Described as a subgenus of Muraenichthys Bleeker. (Type spe- cies; Muraenichthys johnstonensis Schultz and Woods 1949, by original designation.)
DESCRIPTION: General characteristics those of Muraenichthys. Differences include: body stout to moderately elongate, body shorter than tail; posterior nostril opens into mouth; DFO behind anus; pop® absent; teeth absent on vomer, ab- sent or imbedded on intermaxillary, those on maxilla and dentary minute or villiform; SOC absent, SO extends anteriorly to frontals, com- pletely separating parietals; opercular series rudi- mentary, subopercle not produced posteriorly; PG slender; hyoid rudimentary, HH separated from CH by a gap, UH fragmentary, separated medially; gill arches extremely reduced, B: and I»
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absent, UPs-UP4 fused, tooth plates elongate and vermiculated; CTP weakly developed.
ETYMOLOGY: Named for Leonard P. Schultz, ichthyologist, with the assumed noun suffix -idia (feminine).
DISTRIBUTION: Two central and western Pacific species, described as Muraenichthys johnstonen- sis Schultz and Woods, and M. retropinnis Seale.
Subfamily Ophichthinae
DIAGNOSIS: Gill opening variable, mid-lateral to entirely ventral and longitudinal, generally elong- ate and unconstricted; DFO variable, from nape to behind anus; tail tip generally a hard finless point, rudimentary rays visible in certain genera; nasals ossified, generally well developed, but re- duced or absent in certain genera; CH divided into a short median and longer distal portion, the median section connecting to the CH by a car- tilaginous splint (see fig. 17A); UH generally continues posteriorly from basal plate as a slender ossified spike; all branchiostegal rays originate either in association with hyoid or be- fore level of EH tips; gill arch skeleton variably developed, first basibranchial always ossified, second through fourth generally present in either a cartilaginous or rudimentary condition, Cs pres- ent in several genera; coloration variable, band- ed, barred, striped, spotted, or uniform patterns.
Tribe Callechelyini TYPE GENUS: Callechelys Kaup, 1856
DIAGNOSIS: Body (head and trunk) and tail moderately elongate, laterally compressed; body longer than tail; snout acute, rounded at tip; lower jaw included; eye small; posterior nostril opens into mouth; GO low lateral to entirely ventral, converging forward, length much greater than isthmus width; dorsal fin originating on nape; pectoral fin absent; tail tip a hard finless point; head pores reduced, pop*® and tp? absent; LL ossicles nearly continuous; teeth conical, jaw teeth uniserial, those of vomer separated from those of intermaxillary by a gap; skull short, sloping posteriorly, its height ca. 3 or less in its length (fig. 7); orbit moderately developed; SO rounded, without a posterior projection; PG slender, elongate, free and tapering posteriorly; margin of opercular series irregularly ossified, with cartilaginous gaps; suspensorium nearly vertical; otic bulla well developed; hyoid stout; branchiostegal rays numerous; gill arches re-
SERIES 4, V.41,#1 McCOSKER — EELS
duced, C; absent, UP;-UPs separate; pectoral girdle reduced to Cl, SCI, and 1 or 2 rod-shaped elements; IM bones, ribs, and CTP developed; precaudal vertebrae more numerous than caudal; coloration variable, either striped, barred, spot- ted, mottled, or uniform.
REMARKS: The Callechelyini constitute the most distinct and compact of ophichthid tribes. Avail- able material or radiographs of 19 of the 21 spe- cies of Callechelyini has allowed an in depth study of this tribe. The results of two computer- programmed numerical taxonomic evaluations of this tribe are presented in the discussion sec- tion. Several important morphological and osteo- logical characters of the species are listed in Table 8.
Aprognathodon Bohlke
Aprognathodon Bohlke 1966: 99. (Type species; A. platyventris Bohlke 1966, by original desig- nation.)
DESCRIPTION: Anterior nostril tubular; snout moderate, rounded at tip; median groove absent on underside of snout; intermaxillary teeth ab- sent, vomerine teeth present; DFO above SO; anal fin present; 3 supraorbital pores; neuro- cranium well rounded, highest anterior to front- al-parietal suture; hyoid arch very stout, inflex- ible along CH-EH suture; HH absent; branchio- stegal rays numerous, along arch, often joined basally, distal 4-6 rays along EH broadened bas- ally; UH a simple cartilaginous projection pos- teriorly, basal plate ossified; gill arches stout, Hs partially or completely ossified; pectoral girdle contains Cl, SCI, and 2 rod-shaped elements; body coloration strongly banded longitudinally.
ETYMOLOGY: From the Greek XH , without, rf (pro), forward, VVA eos site jaw, and OfavV (odon; masculine), tooth,
reference to the lack of intermaxillary pe.
DISTRIBUTION: A single western Atlantic species, known from the Bahamas through the Lesser An- tilles to Venezuela.
Callechelys Kaup
Callechelys Kaup 1856: 51 (28). (Type species; C. guichenoti Kaup 1856 = Dalophis marmor- ata Bleeker 1853, by monotypy.)
Cryptopterygium Ginsburg 1951: 482. (Type spe- cies; Cryptopterygium holochroma Ginsburg 1951, by original designation.)
PROCEEDINGS CALIFORNIA ACADEMY OF SCIENCES
DESCRIPTION: Anterior nostril tubular; snout short, rounded at tip; a median groove on un- derside of snout (Fig. 32A); intermaxillary and vomerine teeth present; DFO above SO; anal fin present; 3 supraorbital pores; neurocranium well rounded, highest anterior to level of frontal- parietal suture (fig. 7); hyoid arch stout, moder- ately flexible along CH-EH suture; HH separated from CH by a narrow gap; branchiostegal rays numerous, along arch; distal rays along EH broadened basally in some species; UH either a simple slender filament posteriorly, or split into two divergent rays; Hs cartilaginous; pectoral girdle contains Cl, SCI, and either one or two rod-shaped elements; coloration variable, either uniform, spotted, mottled, or banded.
ETYMOLOGY: Kaup (1856a, b) did not give the derivation of the generic name nor did he desig- nate its gender. From his description (1856b: 28), “this handsome eel .. .’”, one must assume that he intended the generic name to be derived from KANNOS (beauty) and € Y LEAVS (enchelys, eel) which is feminine, but according to Liddell and Scott (1801), was later also mascu- line. Bleeker (1865), as first reviser, further con- fused matters by recognizing Dalophis marmor- ata Bleeker as Callechelys marmoratus and also describing Callechelys melanotaenia. To date, the gender of Callechelys has not been estab- lished, although the most recent revisers (McCos- ker and Rosenblatt, 1972) have regarded Calle- chelys as masculine.
DISTRIBUTION: A cosmopolitan genus with 15 tropical and subtropical species. Nominal species include: Callechelys bilinearis Kanazawa (WA), C. cliffi Bohlke and Briggs (EP), C. eristigmus McCosker and Rosenblatt (EP), C. galapagensis McCosker and Rosenblatt (EP), C. /uteus Snyder (IP), C. melanotaenia Bleeker (IP), C. muraena Jordan and Evermann (WA), C. nebulosus Smith (IP), C. perryae Storey (WA, EA), C. striatus Smith (IP), Ophichthys bitaeniatus Peters (IP)*, Crypto- pterygium holochroma Ginsburg (WA), Caecula leucoptera Cadenat (EA)*, Dalophis marmorata Bleeker (IP), Gordiichthys springeri Ginsburg (WA).
REMARKS: Numerous authors (Gunther, 1910: 404; Pellegrin, 1912; Storey, 1939: 63; Smith, 1957: 83; McCosker and Rosenblatt, 1972: 22) have discussed the validity of C. guichenoti, the generic type, with the majority supporting its synonymy with C. marmoratus. Marie-Louise
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Bauchot of the Paris Museum has kindly furn- ished measurements and a radiograph of the type specimen (MNHN 2126) of C. guichenoti. Its morphometry and osteology (183 vertebrae and a single pectoral girdle horizontal element) are further evidence of its synonymy with C. marmoratus.
Subgeneric lines within Callechelys were sug- gested by McCosker and Rosenblatt (1972). They recognized two major groups, one containing species with a simple urohyal and a single rod- shaped pectoral element (fig. 19L) and another with species having the urohyal split posteriorly into two slender divergent rays and two rod- shaped pectoral elements (as in Aprognathodon, fig. 19M). A third can be recognized, which pos- sesses a mosaic of characters, including slightly broadened branchiostegal rays along the epihyal, and urohyal and pectoral girdle conditions that do not conform to either of the above groups. Programs REGROUP and WVGM showed little af- finity between C. nebulosus of this last group and the remainder of the genus. It appears that the simple urohyal, broadened rays, and paired girdle elements are primitive conditions within the Callechelyini, characters shared by C. nebu- losus and C. springeri.
Letharchus Goode and Bean
Letharchus Goode and Bean 1882: 437. (Type species L. velifer Goode and Bean 1882, by original designation.)
DESCRIPTION: Anterior nostril a hole, its rim not raised; snout moderate, acute, not rounded at tip; median groove on underside of snout absent (fig. 32b); intermaxillary and vomerine teeth present; DFO above epiotics; anal fin ab- sent; four supraorbital pores; neurocranium de- pressed, not rounded across parietal-frontal re- gion, highest at frontal-parietal suture; hyoid arch stout, flexible along CH-EH suture, HH sep- arated from CH by a gap; branchiostegal rays numerous, slender, all along arch; UH a slender filament posteriorly; Hs cartilaginous; pectoral girdle contains Cl, SCI, and 2 rod-shaped ele- ments; body coloration uniformly dark, con- trasting strongly with the white dorsal fin.
ETYMOLOGY: From the Greek NMNOEOOMAKC to forget, and ie or (archos; mascu- line), anus, in reference to the lack of an anal fin.
DISTRIBUTION: Known from three New World species: L. velifer from the western Atlantic
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(North Carolina to the northern Gulf of Mexico), L. aliculatus McCosker from off Brazil, and L. rosenblatti McCosker from the eastern Pacific.
REMARKS: The genera Letharchus and Paraleth- archus were recently revised by McCosker (1974). The species of Letharchus form a unique and dis- tinctive offshoot from the generalized callech- elyin condition in their combination of anal fin absence, non-tubular nostrils, an additional supra- orbital pore, and the acute snout, differing mark- edly from the characters of other genera within the tribe. Letharchus pacificus Osborne and Nichols and L. opercularis Myers and Wade are obviously similar to the above species in lacking an anal fin, and probably for that reason were assumed by their describers to be congeneric with L. velifer. After examining considerable material and the types of these five species | have concluded that L. opercularis and L. pacifi- cus represent a separate generic line within the Callechelyini.
The osteological description of Letharchus is based on the eastern Pacific species in that mate- rial of L. velifer was unavailable for dissection.
Leuropharus Rosenblatt and McCosker
Leuropharus Rosenblatt and McCosker 1970: 502. (Type species; L. lasiops Rosenblatt and Mc- Cosker 1970, by original designation.)
DESCRIPTION: Anterior nostril tubular; snout short, rounded at tip; median groove on under- side of snout absent; snout, nape, and much of surface of jaws papillate; intermaxillary teeth present, vomerine teeth absent; DFO above SO; anal fin present; three supraorbital pores; neuro- cranium well rounded, highest anterior to front- al-parietal suture; HH separated from CH by a gap; branchiostegal rays numerous, slender, and along arch; Hs cartilaginous; pectoral girdle con- tains Cl, SCl, and 2 rod-shaped elements; body coloration nearly uniform, median fins white.
La ETYMOLOGY: From the Greek NE VUPOS Ae (leuros), smooth, and ACOs (pharos; neuter), plow, in reference to the toothless vo- mer.
DISTRIBUTION: A_ single species, known only from the type specimen from Manzanillo Bay, western Mexico.
Paraletharchus McCosker
Paraletharchus McCosker 1974: 620. (Type spe- cies; Letharchus pacificus Osburn and Nichols,
SERIES 4, V.41,#1 McCOSKER — EELS
1916, by original designation.)
DESCRIPTION: Anterior nostril tubular; snout short, rounded at tip; median groove on under- side of snout absent; LL ossicles block-like cyl- inders, not heavily fractionated (compare figs. 22H and 221); intermaxillary and vomerine teeth present; GO with a deep anterolateral pocket; DFO above SO; dorsal fin elevated; anal fin ab- sent; three supraorbital pores; neurocranium well rounded, highest anterior to frontal-parietal su- ture; hyoid arch stout, only slightly flexible along EH-CH suture; HH separated from CH by a nar- row gap; branchiostegal rays numerous, along arch, distal rays along epihyal broadened basally; UH a simple slender filament posteriorly; Hs cartilaginous; pectoral girdle contains Cl, SCI, and 2 rod-shaped elements; coloration nearly uniform to mottled.
4 ETYMOLOGY: From the Greek ITAL ERK? (para), near, and Letharchus (masculine), a re- lated genus.
DISTRIBUTION: Known from two eastern Pacific species, P. opercularis (Myers and Wade), a Galapagos endemic, and P. pacificus (Osburn and Nichols), ranging from Baja California to Costa Rica.
REMARKS: As mentioned in the remarks on Letharchus, the above-mentioned species are not congeneric with L. velifer. Schultz and Barton (1960) placed L. opercularis in the synonymy of L. pacificus, however McCosker (1974) provision- ally recognized the Galapagos population as dis- tinct on the basis of the difference in the mean vertebral number (95% confidence limits: P. opercularis 172.7 - 176.6, P. pacificus 158.5 - 162.3).
Tribe Sphagebranchini
TYPE GENUS: Caecula Vahl 1794, the senior ob- jective svnonym of Sphagebranchus Bloch, 1795 (see following remarks).
DIAGNOSIS: Body (head and trunk) and tail moderately elongate, cylindrical, often compres- sed posteriorly; body either nearly equal to or shorter than tail; snout pointed, often broad and depressed; lower jaw included; posterior nostril opens into mouth in most genera; GO entirely ventral; median fins either very low or absent; pectoral fin absent; tail tip sharply pointed; head pores well developed, tp? and pop* gener- ally, and pop* sometimes present; LL ossicles
PROCEEDINGS CALIFORNIA ACADEMY OF SCIENCES
continuous; teeth conical, not caniniform, and generally uniserial; intermaxillary teeth sepa- rated by a gap from those of vomer; neurocran- ium elongate, generally depressed and truncate posteriorly; orbit reduced; otic bulla moderately to well developed; hyoid arch generally slender; branchiostegal rays few to numerous, generally closely associated with hyoid; gill arches re- duced, C; absent in most genera; intramuscular bones, ribs, and caudal transverse processes well developed; precaudal either nearly equal to or more numerous than caudal vertebrae; colora- tion generally uniform, or darker dorsally.
REMARKS: Included among the genera of the Sphagebranchini are the most frustrating and problematical of ophichthid taxa. Their nearly complete lack of superficial characters has re- sulted in a history of repeated lumping and split- ting. Further confusion stems from the inade- quate and misleading descriptions of the two oldest generic names, Caecula Vahl (1794) and Sphagebranchus Bloch (1795). Gosline (1951: 311) summarized the problem in stating that ‘‘the definition, and consequently the limits, of the genus Caecula are agreed upon by no two au- thors as far as | know.”
The tribal name Sphagebranchini is derived from Swainson’s (1838) family name Sphage- branchidae. Swainson’s family name was subse- quently rejected (see page 10) long before Sphagebranchus Bloch (1795) was shown to be a junior objective synonym of Caecula Vahl (1794) (see Bohlke and McCosker, 1975). The family-group name Caeculidae has not appeared in the ichthyological literature. In accordance with Article 40 of the International Code of Zoo- logical Nomenclature (1964), the family-group name Sphagebranchini therefore has priority as the tribal name, with Caecula as the type genus of the tribe.
Achirophichthys Bleeker
Achirophichthys Bleeker 1865: 41. (Type species; A. typus Bleeker 1865, by original designation.)
DESCRIPTION (based on Bleeker, 1865, and Weber and de Beaufort, 1916): Body stout, slightly longer than tail; snout pointed; eye small; anterior nostril not tubular, posterior nos- tril opens into mouth; lips with one row of min- ute tubercular papillae; DFO slightly behind GO; GO low lateral to inferior; teeth conical, long and nearly caniniform anteriorly and along vo- mer, uniserial on vomer, biserial on maxilla.
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W ETYMOLOGY: From the Greek E¢ as (achir), without hands, and Ophichthys, (mascu- line), the amended spelling of Ophichthus.
DISTRIBUTION: A single western Pacific species.
REMARKS: An osteological diagnosis of Achiro- phichthys is not included in this study in that material of A. typus, the generic type, was un- available. A. kampeni (Weber and de Beaufort), its sole described congener, is herein referred to Lamnostoma. Jordan and Davis (1891: 636) sug- gested that A. typus might be the young of Brachysomophis crocodilinus, but subsequent authors have neither accepted nor commented upon this action. Weber and de Beaufort (1916) considered Achirophichthys to be a subgenus of Brachysomophis. This too was ignored by most subsequent authors. Their description of A. typus, based on the type specimen, strongly in- dicates that it is congeneric with A. kampeni, which if true, would place Achirophichthys in the synonymy of Lamnostoma.
Apterichtus Dumeéril
Caecilia Lacépede 1800: 134. Preoccupied by Caecilia Linnaeus, a genus of Amphibia. (Type species; C. branderiana Lacépede 1800, by monotypy.)
Apterichtus Duméril 1806: 331. Also spelled Apterichthys, Apterichthus, Apterichthe, and Apterichtes by other authors. (Type species; Muraena caeca Linnaeus 1758, by monotypy.)
Typhlotes Fischer 1813: 81. A replacement name for Caecilia Lacépede, preoccupied.
Branderius Rafinesque 1815: 93. A replacement name for Caecilia Lacépede, preoccupied.
Ophisurapus Kaup 1856a: 52. (Type species; O. gracilis Kaup 1856, by monotypy.)
Ophisuraphis Kaup 1856b: 29. Emend. pro Oph- isurapus Kaup 1856a.
Verma Jordan and Evermann 1896: 374. (Type species; Sphagebranchus kendalli Gilbert 1889, by original designation.)
?Microrhynchus Blache and Bauchot 1972: 728. Preoccupied by Microrhynchus Dejean 1821, a genus of lepidoptera, as well as mammalia (jourdan 1834), crustacea (Bell 1835), aves (Les- son 1843) and vermes (Kepner 1935). (Type species; Sphagebranchus foresti Cadenat and Roux 1964, by original designation.)
DESCRIPTION: Body very elongate, cylindrical, and pointed at both ends; body and tail nearly subequal; snout pointed, sub-conical, grooved
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and flattened on underside; lips without barbels; eye moderately developed; anterior nostril tubu- lar, posterior nostril a horizontally ovate slit out- side of mouth; GO ventral, converging forward; isthmus short; all fins absent; tp” and pop‘ pres- ence variable among species; teeth pointed, uni- serial in jaws, and largest at intermaxillary which is separated from those of vomer by a short gap; skull slightly depressed, sub-truncate to rounded posteriorly; orbit reduced; nasals and nasal car- tilage developed; SOC short and blunt posteri- orly; maxilla pointed posteriorly; opercular mar- gins entire; suspensorium anteriorly inclined, jaw angle ca. 100°; PG slender, pointed and very reduced; hyoid arch slender, HH separated from CH by a gap; branchiostegal rays closely asso- ciated with hyoid; UH cartilaginous posteriorly; C; absent, UP;-UPs separate; Cl broad, SCI re- duced, Co and Sc absent; posterior trunk parapo- physes with an anterior marginal projection (fig. 33).
ETYMOLOGY: From the Greek AMT fov
(apteron), without fins, and (ichtus, more cor- rectly written ichthys; masculine), fish.
DISTRIBUTION: From 10-12 described and valid species, represented in all tropical oceans. Bohlke (1968) provisionally reviewed the species of Verma (=Apterichtus). The genus Apterichtus can be expanded to include: Muraena caeca Lin- naeus (M), Caecula gymnocelus Bohlke (EP), C. monodi Roux (EA)*, C. equatorialis Myers and Wade (EP), Sphagebranchus klanzingai Weber (IP), S. flavicaudus Snyder (IP), S. kendalli Gilbert (WA), Verma ansp Bohlke (WA), Ophisurapus gracilis Kaup (EA)*, Ophichthys anguiformis Peters (EA)*, and possibly Sphagebranchus for- esti Cadenat and Roux (EA)* and Microrhynchus epinepheli Blache and Bauchot (EA)*.
REMARKS: Blache and Bauchot (1972) recog- nized Verma as distinct from Apterichtus on the basis of a minor difference in posterior nostril location. Through the kindness of Enrico Tor- tonese | have examined a specimen of the Medi- terranean Apterichtus caecus, and have con- cluded that it is clearly congeneric with the At- lantic and Pacific species previously referred to Verma. Microrhynchus Blache and_ Bauchot (1972) is based upon two species known only from the holotypes. Both were unavailable for study. Their sketchy description of the external morphology of the species, upon which the pres- ent study is based, does not provide characters which would allow their generic separation from
SERIES 4, V. 41, #1 McCOSKER — EELS
Apterichtus, or possibly Ichthyapus. Should Mic- rorhynchus prove to be a valid genus a substitute name will be required.
Caecula Vahl
Caecula Vahl 1794: 149. (Type species; C. ptery- gera Vahl 1794, by original designation.)
Sphagebranchus Bloch 1795: 88. (Type species; S. rostratus Bloch 1795 = Caecula pterygera Vahl 1794, by monotypy.)
DESCRIPTION: Body moderately elongate, cylin- drical, compressed posteriorly; body and _ tail nearly subequal; snout pointed, depressed, and broad dorsally, grooved and flattened on under- side; eye moderate; anterior nostril flush with snout anteriorly, produced as a tube posteriorly, posterior nostril associated with a barbel; GO entirely ventral, converging anteriorly, much longer than isthmus, and with an anterolateral duplication forming a deep pouch; DFO slightly behind GO; pop* and tp? present, pop* absent; teeth conical and uniserial, largest at intermaxil- lary which is widely separated from those of vomer; skull depressed, broad, and truncate pos- teriorly; orbit extremely reduced; nasals and nasal cartilage well developed; SOC a short broad point posteriorly; maxilla elongate, pointed posteriorly; coranoid process of articular moder- ately enlarged; operculum well developed, pre- operculum narrow and thin, their margins entire; suspensorium nearly vertical; hyomandibular broad, expanded posterodorsally and anteriorly, strongly ridged; otic bulla weakly developed; PG slender, pointed at each end, and braced against hyomandibular by a posteromedial extension; hyoid arch slender; HH separated from CH by a gap; branchiostegal rays numerous, flat and unbranched, loosely associated with hyoid; out- ermost rays along epihyal slightly broadened; UH a slender filament posteriorly; C; absent, UP3-UPs separated, anterior half of Bi ossified; Cl, SCI, Sc and Co present.
ETYMOLOGY: A diminutive of the Latin caecus, blind, regarded as feminine.
DISTRIBUTION: Two western Pacific species.
REMARKS: Various species have been haphazard- ly assigned to Caecula to such an extent that it has become a catch-all for most finned and fin- less ophichthids lacking pectoral fins. Smith (1964) redescribed the type of C. pterygera and began the dissection of this confusing assemb- lage. Smith erred in presuming C. pterygera and
PROCEEDINGS CALIFORNIA ACADEMY OF SCIENCES
Lamnostoma pictum to be synonymous, and in fact, congeneric. Osteologically these genera are similar in their coronoid processes, hyoid, gill arch, and nostril conditions, but differ tren- chently in their neurocrania.
Blache and Bauchot (1972) placed the type species of Sphagebranchus, S. rostratus Bloch, in Caecula. BOhlke and McCosker (1975) considered the type species of those genera to be conspe- cific, and suggested that the collection locality of S. rostratus (“river in Surinam’’) was erroneous.
Cirricaecula Schultz
Cirricaecula Schultz 1953: 49. Type species; C. johnsoni Schultz 1953, by original designa- tion.)
DESCRIPTION: General characters those of /Ich- thyapus. Differences include: body and tail near- ly subequal; numerous cirri along edge of upper lip, a prominent barbel between the nostrils; an- terior nostril nearly flush with snout anteriorly, slightly produced as a tube posteriorly; GO en- tirely ventral, consisting of 2 parallel longitudinal slits with thin medial membranes; isthmus min- ute; pop’ and tp? present; otic bulla weakly de- veloped; PG slender, pointed at each end; hyoid arch slender, HH separated from CH by a gap, UH a slender filament posteriorly; Cs; ossified, UP;-UP, fused; pectoral girdle reduced to a ven- trally located Cl pair which are broad and anteri- orly expanded (fig. 19); CTP strongly developed.
ETYMOLOGY: From the Latin cirrus, tendril, and Caecula (feminine), a related genus.
DISTRIBUTION: A single central Pacific species, known only from the type series collected at Eniwetok, Marshall Islands.
Hemerorhinus Weber and de Beaufort, incertae sedis
Hemerorhinus Weber and de Beaufort 1916: 280. (Type species; Sphagebranchus heyningi Web- er 1913, by original designation.)
DESCRIPTION: Body moderately elongate, cylin- drical, pointed at each end; body longer than tail; snout pointed, grooved on underside; eye small; anterior nostril flush with snout; posterior nostril below eye, a long slit in upper lip; GO inferior, vertical; vertical fins low; tp? present(?), pop® absent(?).
/ ETYMOLOGY: Presumably from the Greek 72 ME efi (hemeros), cultivated, and eC C EI 6
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(rhinos; masculine in accordance with item 30(a)(3) of the International Code of Zoological Nomenclature), nose.
DISTRIBUTION: Known from the type specimen, collected in deep water (69-91 meters) from Flores, Indonesia, and H. opici Blache and Bau- chot (EA)*.
REMARKS: Species of Hemerorhinus were un- available for study. Blache and Bauchot’s (1972) redescription of the type species clarified several confusing aspects of the original description, par- ticularly in correcting the mistaken intepretation of the nostrils and fin position. From their dis- cussion however, | am unable to confidently find its placement within this tribe. On the basis of Blache and Bauchot'’s illustrations, the cephalic pore condition would indicate a similarity to the species of Yirrkala.
Ichthyapus de Barneville
Ichthyapus de Barneville 1847: 219. (Type spe- cies; /. acutirostris de Barneville 1847, by monotypy.)
Rhinenchelys Blache and Bauchot 1972: 718. (Type species; Sphagebranchus ophioneus Evermann and Marsh 1902, by original desig- nation.)
DESCRIPTION: Body elongate, cylindrical, point- ed at both ends; tail longer than body; snout pointed, depressed, and broad dorsally, grooved and flattened on underside; lips without barbels; eye small; anterior nostril flush with snout, pos- terior opens into mouth; GO entirely ventral, with a thin medial membrane, converging for- ward, isthmus small; all fins absent; tp? always and pop? usually present; teeth pointed, uni- serial, and largest at intermaxillary which are separated from those of vomer by a gap; skull depressed, broad, and truncate posteriorly (fig. 8); orbit extremely reduced; nasals moderately, and nasal cartilage well developed; SOC moder- ately projecting posteriorly; maxilla elongate and pointed posteriorly; suspensorium nearly verti- cal; opercular margins entire, preopercle re- duced; hyomandibular broad, expanded anteri- orly and posterodorsally; otic bulla moderately developed; PG elongate and rectangular posteri- orly, with a slender projection from the antero- dorsal corner; hyoid thickened (not as slender as in related genera); HH separated from CH by a narrow gap; branchiostegal rays not numerous, slender and generally unbranched, closely asso-
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ciated with hyoid, outermost rays along EH broadened basally; UH cartilaginous for pos- terior two-thirds; C; reduced (see Remarks), UP3- UP, separate; Cl broad, SCI usualy absent, Sc and Co absent; posterior trunk parapophyses with an anterior marginal projection as in Apter- ichtus (fig. 33).
ETYMOLOGY: From the Greek ¢Y% Obs (ichthys), fish, and Gx ae) Sp (apous; masculine), without foot, presumably in _refer- ence to the lack of pectoral fins.
DISTRIBUTION: Circumtropical, with 6-7 valid species. Included are: /. acutirostris de Barneville (locality unknown)*, Sphagebranchus — vulturis Weber and de Beaufort (=Caecula platyrhyncha Gosline) (IP), S. ophioneus Evermann and Marsh (WA), Apterichthys selachops Jordan and Gilbert (EP), and three undescribed eastern and western Pacific forms. Incertae sedis: Sphagebranchus omanensis Norman (IP).
REMARKS: The sharp-snouted finless species pre- viously placed in Sphagebranchus, excluding the species of Cirricaecula and Apterichtus as herein defined, are referred to Ichthyapus. The generic type, /. acutirostris, is obviously congeneric with those species according to descriptions of the type made by de Barneville (1847, fide Fowler, 1936: 293), Kaup (1856b: 29) and Blache and Bauchot (1972: 718-728).
Blache and Bauchot (1972) differentiated Rhinenchelys from Ichthyapus on the basis of minor differences in nostril condition and inter- maxillary tooth location. My examination of the osteology of ophioneus, the type of Rhinench- elys, indicates that it is congeneric with sela- chops, vulturis, and presumably acutirostris.
Nelson (1966a: table 1, figure 19) has de- scribed and illustrated the gill arch condition of I. vulturis (as Caecuia platyrhyncha). The fifth ceratobranchial (Cs) is reduced and fused to the lower pharyngeal dermal tooth plate. | have found the gill arches of J. ophioneus, |. vulturis, and /. selachops to be similar in this condition. Cirricaecula, with a prominent Cs, appears inter- mediate between /Ichthyapus and most Ophich- thyini in this condition. The C; condition of the related genus Apterichtus, based on my examina- tion of A. flavicaudus, is the most reduced in the group.
Lamnostoma Kaup
Lamnostoma Kaup 1856: 49 (23). (Type species; L. pictum Kaup 1856 = Dalophis orientalis
SERIES 4, V.41,#1 McCOSKER — EELS
McClelland 1844, by Jordan 1919b as first re- viser.)
Anguisurus Kaup 1856: 50 (24). (Type species; A. punctulatus Kaup 1856 = Dalophis orien- talis McClelland 1844, by monotypy.)
DESCRIPTION: Body stout, cylindrical, pointed at each end; body slightly longer than tail; snout pointed, its underside grooved; eye small to moderate; anterior nostril flush along snout, its posterior rim produced, posterior nostril usually associated with a pendulous flap; GO inferior, ca. equal to isthmus; DFO above or behind GO; tp? and pop? absent; teeth slender, pointed, and recurved, uniserial or biserial in jaws, those of intermaxillary and vomer largest and _ widely spaced; neurocranium truncate posteriorly, elongate and narrow, particularly along ethmoid and interorbital region; orbit depressed; nasals and nasal cartilage moderately developed; SOC present; maxillae moderately elongate, slender but not pointed posteriorly; coronoid process of articular greatly enlarged; opercular series mod- erately developed, their margins entire; suspen- sorium anteriorly inclined, jaw angle ca. 100°; hyomandibular broad, expanded posterodorsally and strongly ridged; otic bulla well developed; PG slender, very reduced; hyoid slender, equal to branchiostegal rays in thickness, HH separated from CH by a broad gap, rays numerous, flat and unbranched, only the distal-most associated with hyoid, others terminate anteriorly behind tip of slender UH, outermost rays along EH slightly broadened; gill arches reduced, C; absent, UPs- UP, separate, B; cartilaginous except at anterior tip which is ossified; Cl, SCI, and reduced Co and Sc present; coloration generally darker dor- sally, a series of white spots across nape.
ETYMOLOGY: From the Greek AMX AL CX
(lamna), a horrible anthropophagous monster, a bugbear used by the Greeks to frighten refract- ory children (Jordan and Evermann, 1896: 49), and g TO (stoma; neuter), mouth.
DISTRIBUTION: From the western Pacific, pro- visionally including four species.
REMARKS: Lamnostoma has been placed by re- cent authors in the synonymy of Caecula. It is herein found to differ markedly in numerous osteological and morphological characters, and is COnsequently resurrected. The species of this genus are generally collected in freshwater, and are easily recognized by their slender jaws and conspicuous white spotting on the head and
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lateral line. Several nominal species are included in Lamnostoma, most of which fall into the syn- onymy of L. orientalis (McClelland). Caecula min- dora Jordan and Richardson and C. tay/ori Herre are also referable to this genus. Achirophichthys kampeni (Weber and de Beaufort) is clearly a Lamnostoma. Its description, and recent refer- ences containing general morphological descrip- tions (Herre, 1924; Nichols, 1955; La Monte, 1961; Tortonese, 1964), concern large adults which have been collected in freshwater, each displaying the slender jaws and the head and body spotting of Lamnostoma.
Stictorhinus Bohlke and McCosker
Stictorhinus Bohlke and McCosker 1975: 5. (Type species; S$. potamius Bohlke and McCos- ker 1975, by original designation.)
DESCRIPTION: General characteristics those of Ichthyapus. Differences include: Median fins present, low but distinct, DFO ca. mid-trunk; tp? present, pop* absent; LL ossicles with a short gap at pores; basisphenoid not elongate as in Ichthyapus (compare Figs. 8 and 9); SOC re- duced; opercular series reduced, interopercle absent, preopercle reduced; branchiostegal rays numerous, branched basally in some individuals, closely associated with hyoid, outermost rays along EH broadened basally; UH a slender ossi- fied filament posteriorly; C; absent; Cl broad and expanded anteriorly, SCI absent, Sc and Co reduced; trunk parapophyses lack an anterior projection (fig. 33).
ETYMOLOGY: From the Greek TTLKTOS (stiktos), pricked or punctured, and eC Llp
(rhin, latinized to rhinus, nominative case), nose, in reference to the nature of the anterior nostrils.
DISTRIBUTION: A single western Atlantic species, known from tidal rivers in Brazil.
REMARKS: In 1971 Naercio Menezes sent the author a series of eels from freshwater in Brazil. These were identified as Sphagebranchus rostra- tus Bloch, a species known only from the type specimen said to have been from a “river in Suri- nam.”” Subsequent examination of the type speci- mens of Caecula pterygera and Sphagebranchus rostratus by J. E. BOhlke found them to be based on the same species, and the Brazilian specimens to be an undescribed genus and species (Bohlke and McCosker, 1975). My treatment (McCosker, 1973) of Sphagebranchus was therefore based on Stictorhinus.
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Yirrkala Whitley
Yirrkala Whitley 1940: 410. (Type species; Y. chaselingi Whitley 1940 = Sphagebranchus lumbricoides Bleeker 1865, by original desig- nation.)
Pantonora Smith 1964: 719. (Type species; Oph- ichthys tenuis Gunther 1870, by original desig- nation.)
DESCRIPTION: Body elongate, cylindrical, shorter than tail; snout conical, moderately developed, its underside grooved; eye moderate; anterior nostril in a short tube, posterior opens into mouth; GO ventral, longer than isthmus; DFO above or slightly behind GO; tp” usually present, pop® absent; teeth conical, pointed, nearly sub- equal, uniserial in jaws, those on vomer biserial anteriorly, separated from those of intermaxillary by a gap; skull not depressed, rounded posteri- orly; orbit not strongly depressed; nasals and nasal cartilage moderately developed; SOC ab- sent; maxilla pointed posteriorly; opercular ser- ies well developed, their margins entire; sus- pensorium anteriorly inclined, jaw angle ca. 100°; PG slender, pointed anteriorly; HH sepa- rated from CH by a short gap (HH absent in Y. misolensis); branchiostegal rays closely associ- ated with hyoid; UH with a short projection pos- teriorly; C; absent, UP3-UPs separate; pectoral girdle contains SCI, Cl, and reduced Co and Sc; posterior trunk parapophyses lack anterior mar- ginal projections.
ETYMOLOGY: Named for Yirrkala, northern Aus- tralia, the type locality of the type species, mas- culine, in accordance with item 30(b)(ii) of the International Code of Zoological Nomenclature.
DISTRIBUTION: Contains approximately 12 spe- cies, from the eastern Atlantic, the Red Sea, and Indian and western Pacific Oceans. Included are: Sphagebranchus lumbricoides Bleeker, Ophich- thys tenuis Gunther, Caecula maculata Klause- witz, and an undescribed species from the Mar- quesas. Incertae sedis: Sphagebranchus macro- don Bleeker*, S. gjellerupi Weber and de Beau- fort*, S. kaupi Bleeker, Dalophis moluccensis Bleeker*, Ophichthys misolensis Gunther, Mur- aena fusca Zuiew*, and Caecula natalensis Fow- ler*.
REMARKS: The description of Yirrkala is so lack- ing in diagnostic characters as to preclude its proper placement, and consequently has been ignored by most recent authors. The only sub- sequent reference to Y. chaselingi, the generic
70
type, which | have encountered is that of Munro (1957) in which this species is placed in Sphage- branchus. | have examined and x-rayed the badly damaged and dessicated paratype of Y. chase- lingi. The anterior nostrils, head pores, and gill openings are too badly damaged to allow accur- ate examination, however the dentition is well preserved and agrees well with Whitley’s illus- tration. In his description, Whitley stated that Y. chaselingi and Sphagebranchus lumbricoides are congeneric, differing in the ‘position of dorsal origin, proportion of head to trunk, in having vomerine teeth largest, and other details of porportions and dentition.” My comparison of the paratype of Y. chaselingi and specimens of S. lumbricoides from Vietnam (CAS 13969) and the Philippines (CAS reg. 1607) indicates that they are conspecific. The proportions, dorsal fin origins, dentition, and vertebral numbers (Y. chaselingi = 153, S. lumbricoides = 151,154) are not different.
Pantonora Smith (1964) is herein considered a synonym of Yirrkala.
Sphagebranchus kaupi and Ophichthys misol- ensis are provisionally referred to Yirrkala. Y. kaupi differs in having the major axis of its GO vertical. Y. misolensis differs in having basihyals fused to the ceratohyals, lateral line ossicles con- sisting of numerous short coils rather than small block-like segments, and lacking tp.
The external morphology of the species of Hemerorhinus, as described by Blache and Bau- chot (1972), indicates that those species might be conspecific with the species within this com- plex. A comparative study of the type species of Yirrkala, Hemerorhinus, and Pantonora is clearly needed.
Tribe Bascanichthyini
TYPE GENUS: Bascanichthys Jordan and Davis, 1892.
DIAGNOSIS: Body (head and trunk) and tail moderately to extremely elongate, generally cyl- indrical, and compressed posteriorly in some genera; body either equal to or longer than tail; lower jaw included; posterior nostril opens into mouth; GO low lateral, crescentric, never en- tirely ventral; median fins generally low, DFO on head in most genera; pectoral fin absent or present as a minute flap in upper GO corner; head pores reduced, pop* and tp? absent; LL ossicles nearly continuous or separated by a short gap at pores; teeth conical, not caniniform;
SERIES 4, V.41,#1 McCOSKER — EELS
neurocranium variable in proportions and pos- terior shape; orbit generally reduced; otic bulla moderately to well developed; hyoid condition variable; branchiostegal rays numerous, associ- ated with the hyoid; gill arches reduced, Cs; ab- sent in most genera; IM bones, ribs, and CTP developed; precaudal vertebrae generally more numerous than caudal; coloration nearly uni- form, or darker posteriorly.
Allips McCosker
Allips McCosker 1972: 116. (Type species; A. concolor McCosker 1972, by original designa- tion.)
DESCRIPTION: Body elongate, cylindrical for most of its length; body much longer than tail; head markedly rugose; snout blunt, its under- side grooved; eye small; anterior nostril tubular; GO oblique, lateral, and less than isthmus in length; median fins low, DFO in anterior trunk region; pectoral minute; caudal blunt; tip of snout with numerous sensory hairs; LL ossicles nearly continuous; teeth small, conical, uniserial, intermaxillary teeth largest, separated from those of vomer; skull sloping posteriorly, orbit a narrow slit; SOC weakly developed; maxillae taper posteriorly; HH separated from CH by a gap; branchiostegal rays numerous, slender; pec- toral girdle reduced, only Cl, SCI, and a thin Co (2).
yA ETYMOLOGY: From the Greek & VAOS (allos), another, and oe yy (ips; mascu- line), a worm.
DISTRIBUTION: A_ single species, known only from the type specimen from Thailand.
Bascanichthys Jordan and Davis
Bascanichthys Jordan and Davis 1891: 621. (Type species; Caecula bascanium Jordan 1885 = Sphagebranchus teres Goode and Bean 1882, by original designation.)
DESCRIPTION: Body elongate, cylindrical, and compressed posteriorly; body longer than tail; head markedly rugose; snout short and blunt, its underside grooved; mouth small; eye small; anterior nostril tubular; GO nearly horizontal, low lateral, = isthmus in length; median fins low, DFO on head; pectoral minute; caudal blunt; LL ossicles nearly continuous; teeth small, conical, uniserial in jaws, intermaxillary teeth separated from those of vomer by a short gap; neurocranium sloping posteriorly (fig. 10), orbit
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reduced; nasals and nasal cartilage moderately developed, the nasals closely associated with the ethmoid for their entire length; SOC absent; maxilla weak, slender, and pointed posteriorly, attached before mid-vomer (fig. 16); opercular series moderately developed, their margins en- tire; suspensorium nearly vertical; otic bulla moderately developed; PG pointed anteriorly; HH separated from CH by a narrow suture; branchiostegal rays numerous, often branched basally, all along arch, the distal rays not broad- ened basally; UH either ossified or cartilaginous posteriorly; C; reduced or absent, UPs3-UPs sep- arate; pectoral girdle consists of reduced Cl, SCI, Sc and Co.
ETYMOLOGY: From Bascanion (diminutive, from the Greek 32a 7K X vos , malignant), the generic name for the black snake, and
oe e&f (ichthys; masculine), fish.
DISTRIBUTION: All tropical oceans, with ap- proximately 16 presently recognized species, in- cluding an undescribed eastern Pacific species from Cocos Island. Included are: B. bascanoides Osburn and Nichols (EP), B. cylindricus Meek and Hildebrand (EP), B. panamensis Meek and Hilde- brand (EP), B. ceciliae Blache and Cadenat (EA)*, B. congoensis Blache and Cadenat (EA)*, B. paul- ensis Storey (WA), B. pusillus Seale (IP)*, Sphage- branchus teres Goode and Bean (WA), S. longi- pinnis Kner and Steindachner (IP)*, S. scuticaris Goode and Bean (WA)*, Callechelys myersi Herre (IP), Ophichthys filaria Gunther (IP)*. I/Incertae sedis: Callechelys longissimus Cadenat and Mar- chal (EA)*, and Ophichthys kirkii Gunther (IP)*. Leptenchelys tenuis Tortonese, from New Guinea, is probably a junior synonym of B. longipinnis.
REMARKS: The species of Bascanichthys have been reviewed by Storey (1939), Ginsburg (1951) (western Atlantic), and Blache and Cadenat (1971) (eastern Atlantic). The status of Bascanichthys pusillus, considered a junior synonym of B. filaria by Fowler (1931: 316), is uncertain.
Caralophia Bohlke
Caralophia Bohlke 1955: 1. (Type species; C. loxochila Bohlke 1955, by original designa- tion.)
DESCRIPTION: Body elongate, cylindrical, mod- erately compressed posteriorly; body longer than tail; snout subconical, blunt from above, lacking a groove on its underside; eye moderate; anter- ior nostril non-tubular, a hole with lateral projec-
ail
tions into it; GO ventral, converging forward, longer than isthmus; median fins low, DFO on head; tail tip pointed; LL narrowly separted at pores; teeth bluntly conical, uniserial in jaws and on vomer, intermaxillary teeth slightly larger, separated from those of vomer by a short gap; skull sloping posteriorly, depressed dorsally, or- bit reduced; nasals stout and well developed, their margins entire, tightly joined to ethmoid; nasal cartilage well developed; frontals extend posteriorly to mid-parietals; SOC moderately de- veloped, SO extends from mid-frontals posteri- orly to a strong point; maxilla weak, slender, and pointed posteriorly; opercular series developed, their margins entire; suspensorium posteriorly inclined, jaw angle ca. 100°; otic bulla moder- ately developed; PG broad centrally, closely as- sociated with maxilla anteriorly; hyoid stout, HH fused to CH; branchiostegal rays numerous, along arch, and often branched basally; distal rays along EH broadened basally; UH reduced to a well ossified basal plate with a posterior car- tilaginous filament; tooth plates reduced, UP3-UP4 fused; pectoral girdle reduced to a Cl and frag- ments of a SCI, Sc, and Co.
ETYMOLOGY: From the Greek KX PK , head, and NAO Pf cot (lophia; feminine), a mane, in reference to the anterior dorsal fin origin.
DISTRIBUTION: A single western Atlantic spe- cies, extending from the Bahamas to the lesser Antilles and Panama.
Dalophis Rafinesque
Dalophis Rafinesque 1810a: 68. (Type species; D. serpa Rafinesque 1810a = Sphagebranchus imberbis De la Roche 1809.)
Pterurus Rafinesque 1810b: 59. (Type species; P. flexosus Rafinesque 1810b = Sphagebranch- us imberbis De la Roche 1809, by monotypy.)
Scytallurus Duméril 1856: 199. (Type species; Sphagebranchus imberbis De la Roche 1809, by monotypy.)
Pelia Bleeker 1863: 128. (Type species; P. cepha- lopeltis Bleeker 1863.)
DESCRIPTION: Body moderately elongate, cyl- indrical, slightly compressed posteriorly; _ tail longer than body; snout sub-conical, grooved on underside; eye small; anterior nostril tubular; GO low on body, extending onto venter, its length ~ isthmus; vertical fins low, DFO well behind GO; pectoral fin rudimentary if present; tail tip blunt; LL ossicles widely separated at
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pores; teeth conical, uniserial, intermaxillary teeth separated from those of vomer by a gap; skull subtruncate posteriorly, orbit depressed; nasals well developed; SOC weakly developed; maxilla tapers posteriorly; suspensorium nearly vertical; HH separated from CH by a gap; UH ossified posteriorly; gill arches stout, Hs ossified, C; a slender ossified rod, UP3-UPs separate; pec- toral girdle reduced, only a Cl and SCI present.
ETYMOLOGY: The significance of the prefix is not obvious, but possibly derived from Dalmatia, then a country on the east side of the Adriatic Sea, and ro) na (ophis; masculine), a snake.
DISTRIBUTION: Five eastern Atlantic and Medi- terranean species are presently recognized, in- cluding: D. boulengeri Blache and Bauchot (EA)*, D. multidentatus Blache and Bauchot (EA)*, D. obtusirostris Blache and Bauchot (EA)*, Pelia cephalopeltis Bleeker (EA)*, and Sphagebranchus imberbis De la Roche (M).
REMARKS: Blache and Bauchot (1972) have re- cently expanded Dalophis to include Pelia and five nominal species. Their finding (p. 746) that the pectoral fin, though generally absent, may be represented by a ‘miniscule filament’ is in agreement with Lozano Rey’s (1947, p. 546). Through the kindness of Enrico Tortonese | have been able to examine and partially dissect a specimen of Dalophis imberbis. A complete os- teological preparation, however, was impossible.
Dalophis has been summarily synonymized with Caecula by previous authors. Its general facies (physiognomy, low median fins, and body depth and taper) and certain osteological fea- tures (dentition, pectoral girdle, and anterior trunk vertebrae) suggest a relationship with Ethadophis and Leptenchelys, genera restricted to the east- ern Pacific. The gill arch skeleton and body/tail proportions are typically ophichthin, and for that reason, Dalophis is placed in the Bascanichthyini with reservations.
Ethadophis Rosenblatt and McCosker
Ethadophis Rosenblatt and McCosker 1970: 498. (Type species; EF. byrnei Rosenblatt and Mc- Cosker 1970, by original designation.)
DESCRIPTION: Body moderately elongate, cyl- indrical anteriorly, becoming compressed pos- teriorly; body equal to or slightly longer than tail; snout rounded, conical from above; eye small; anterior nostril tubular; GO low on body,
SERIES 4, V. 41, #1 McCOSKER — EELS
extending onto venter, their length = to isthmus; vertical fins low, DFO before GO; tail tip blunt, fleshy in one species; LL ossicles separated at pores; teeth conical, uniserial, intermaxillary teeth separated from those of vomer by a gap; skull subtruncate posteriorly, orbit depressed; nasals well developed; SOC moderately devel- oped, pointed as in Bascanichthys; maxilla tap- ers posteriorly; suspensorium nearly vertical; HH separated from CH by a gap; branchiostegal rays numerous, slender and along hyoid; UH ossified posteriorly; UP3-UP,s separate; pectoral girdle re- duced, only a Cl, SCI, and Co (?) remnant visible by radiograph.
Zz ETYMOLOGY: From the Greek cen (ethas), customary or ordinary, and O PoG (ophis; masculine), serpent.
DISTRIBUTION: Two species, £. byrnei Rosen- blatt and McCosker and £. merenda Rosenblatt and McCosker, known only from the type speci- mens from Baja California, Mexico.
Gordiichthys Jordan and Davis
Gordiichthys Jordan and Davis 1891: 644 (Type species; G. irretitus Jordan and Davis 1891, by original designation.)
DESCRIPTION: Body extremely elongate, cylin- drical, much longer than tail; snout tapering; eye moderate; GO low lateral; DFO behind nape: teeth conical, recurved, and uniserial.
ETYMOLOGY: From Gordius, the horsehair worm, named after I-76 P Alos, the king whose complicated knot was cut by Alexander, and ox evr (ichthys; masculine), fish.
DISTRIBUTION: Known from a single deep-water western Atlantic species.
REMARKS: The above description is based on Jordan and Davis (1891) and Ginsburg (1951) in that material of G. irretitus, the type species, was unavailable for study. Gordiichthys will be rede- scribed by J. E. Bohlke (personal communication). G. springeri Ginsburg, its sole described con- gener, is a species of Callechelys (fide Rosenblatt and McCosker, 1970, and McCosker and Rosen- blatt, 1972).
Leptenchelys Myers and Wade
Leptenchelys Myers and Wade 1941: 72. (Type species; L. vermiformis Myers and Wade 1941, by original designation.)
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DESCRIPTION: Body elongate, cylindrical, slightly compressed posteriorly; body longer than tail; snout short, subconical; top of head and snout covered with numerous papillae; eye small; an- terior nostril tubular; GO low lateral, crescentic, = isthmus; DFO on head; median fins conflu- ent around tail tip; teeth weak, pointed, uni- serial; skull sloping posteriorly, orbit reduced; SO rounded, not projecting posteriorly; suspen- sorium anteriorly inclined, jaw angle ca. 100°; hyoid arch slender, HH separated from CH by a narrow gap: branchiostegal rays slender, appear from radiograph to lie along hyoid; pectoral girdle reduced, only SCI and Cl visible in radio- graph.
ETYMOLOGY: From the Greek NEMTTOS (leptos), thin, and é YK ENS (enchelys; either feminine or masculine, treated as mascu- line), eel.
DISTRIBUTION: A _ single species, known only from the type specimen from Playa Blanca, Pacific Costa Rica.
REMARKS: This poorly known genus is provision- ally referred to the Bascanichthyini. The generic type, apparently uncollected since the capture of the 115 mm type specimen, was examined and radiographed for the purpose of this study. Its inclusion as a bascanichthyin is based on the numerous branchiostegal rays which appear to contact the hyoid, the posteriorly sloping neuro- Cranium, the low unconstricted gill openings, and the head pore configuration. Caudal fin rays are present on the type specimen, but are more poorly developed than any myrophine’s.
Leptenchelys has had an erratic history. Origi- nally placed in the Echelidae on the basis of its having a caudal fin (Myers and Wade, 1941), it was then synonymized with Muraenichthys by Schultz and Woods (1949), re-erected and ex- panded by Schultz, et al. (1953), and finally, re- stricted to a single species (McCosker, 1970) differing markedly from Muraenichthys and re- lated genera. Leptenchelys tenuis Tortonese (1964) from New Guinea is a species of Bascan- ichthys, which is possibly synonymous with B. longipinnis described from Samoa. My exami- nation of the holotype of L. tenuis indicates that Tortonese overlooked the rudimentary pectoral fin, similarly developed in B. longipinnis accord- ing to Storey (1939). The tail tip of L. tenuis is soft and fleshy, but not unlike that of other species of Bascanichthys.
7k)
Phaenomonas Myers and Wade
Phaenomonas Myers and Wade 1941: 77. (Type species; P. pinnata Myers and Wade 1941, by original designation.)
DESCRIPTION: Body elongate, cylindrical, much longer than tail; head markedly rugose; snout blunt, grooved ventrally; eye minute; anterior nostril tubular; GO low lateral, oblique and
elongate, = isthmus; DFO mid-head, low, end- ing in anterior trunk region; anal fin absent; teeth small, conical, uniserial, intermaxillary
teeth largest, separated from those of vomer; skull sloping posteriorly, orbital foramen a_nar- row slit; nasal cartilage weak; SOC weakly de- veloped; maxilla tapers