Notes on the Systematic Status of the Eels Neenchelys and Myroconger GARETH J
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Notes on the Systematic Status of the Eels Neenchelys and Myroconger GARETH J. NELSONl N eencbelys . Xenocongridae, Dysomminidae, and Muraeni BOHLKE (1960) SUGGESTED that eels of the dae (N elson, 1966b) . In completely lacking genus N eenchelys possibly have overlapping basibranchials, the arches of M yroconger differ branchiostegal rays and that, if they did,they from those of H eterencbelys, Anguilla, and should be assigned to the family Ophichthidae. M oringua, but resemble those of xenocongrids, Nelson (1966a) described the osteology of Dysommina, and muraenids. In lacking a second N eenchelys buitendijki, confirming the presence pharyngobranchial they are unlike xenocon of overlapping branchiostegal rays, and for this grids , but resemble Dysommina and muraenids. and other reasons referred the genus N eenchelys Like that of Dysommina the fourth arch of to the family Ophichthidae, subfamily Eche M yroconger is not appreciably enlarged and linae. The present report, based on an ex "pharyngeal jaws" like those of muraenids do amination of the holotype of Neenchelys micro not occur. Thus, the arches of M yrocol1ger are tretus, confirms the presence of overlapping most like those of Dysommina. The most nota branchiostegal rays in the type species of N een ble differences include the presence in M yro chelys. Like those of N . buitendijki (Nelson, conger of third hypobranchials (a primitive 1966a, fig. 2A), those of N . microtretus in feature) and the apparent absence of fifth clude six rays articulating with the dorsal por ceratobranchials (an advanced one) . tion of the ceratohyal and more than 25 others What could be learned of the pharyngeal widely overlapping in the midline. musculature also suggests a relationship with the more advanced eels of the anguilloid lineage, for a subpharyngealis occurs, as it does at least M yroconger in M oril1 gua, Kaupichthys, and muraenids, and Thi s genus and the family it represents ap retractor muscles have a small area of origin on parently are known only from the holotype of the vertebral column, foreshadowing the large M yroconger compressus. The specimen had area of origin in some muraenids (N elson, been partly dissected, leaving the gill arches 1967) . exposed, which allowed the following observa These observations of M yroconger complete tions to be made: third and fourth upper a review of gill arch structure for the families ph aryngeal tooth plates separate; first and sec of anguilloid eels (N elson, 1966b). Within ond pharyngobranchials absent, the third sup this group, on the basis of gill arch structure porting the tooth plates; basibranchials absent; there seem to be three main lines of specializa independent rodlike hypobranchials in arches tion, each characterized by reduction of the gill one-three, those of the third cartilaginous; arch skeleton : one leads toward the Morin fourth ceratobranchials not extended anteriorly, guidae, another toward the Muraenidae, the not separating the third arches of either side; other toward the Cyemidae. If the anguilloid fifth ceratobranchials apparently absent; ventral eels are given the status of a suborder, these parts of the arches not meeting in the midline. lines of specialization could be given the status M yroconger has the frontal bones separated of superfamilies. However, on the basis of gill by a suture and therefore belongs to the anguil arch structure alone it is difficult to distinguish loid lineage of Regan (1912) , including the between generalized members of these different Heterenchelidae, Anguillidae, Moringuidae, lines, or to decide which if any Recent forms can be considered generalized muraenoids. 1 Department of Paleozoology, Swedish Museum of Consequently, the following synopsis is offered N atural H istory, Stockholm 50, Sweden. Manuscript received January 20, 1967. Present address: Ameri more as a working hypothesis than as a final can Museum of N atural History, Ne w York, N .Y. classification: 562 Neencbelys and Myroconger-NELsoN 563 Caudal fin continuous with dorsal and anal; at the British Museum (Natural History) while no pelvic fins; frontal usually paired . I was on an NSF postdoctoral fellowship. ... .. .. .. suborder Anguilloidei a. Jaws not produced ; gill arch skeleton in REFERENCES cluding at least rudimentary basibranchials BOHLKE, J. E. 1960. A New Ophichthid Eel of · . .. .. .. .. superfamily Anguilloidae the Genus Pses domyropbis from the Gulf (including families Heterenchelidae, An of Mexico. N otulae Naturae 329, 8 pp., 2 guill idae, Moringuidae) figs. b. Jaws not produced; gill arch skeleton with- NELSON, G. J. 1966a. Osteology and relation out basibranchials . ships of the eel, N eencbelys buitendijki . · . .. .. .. superfamily Muraen oidae Copeia 1966(2) :321-324, 2 figs. (including Xenocongridae, Dysomminidae, --- 1966b. Gill arches of teleostean fishes Myrocongridae, Muraenidae) of the order Angui lliformes. Pacific Sci. c. Jaws produced. "gill arch skeleton with or 20(4 ) :391-408, 58 figs. without basibranchials . - - - 1967 . Branchial muscles in repre · superfamily Nemichthyoidae sentatives of five eel families. Pacific Sci. (including Serrivomeridae, Nem ichthyidae, 21 (3) :348-363. Cyemidae) REGAN, C. T. 1912 . The osteology and classi fication of the teleostean fishes of the order Observations on type specimens were made Apodes. Ann . Mag. Nat. Hist., Ser. 8, 10: through the courtesy of Dr. P. H . Greenwood 377-387, 2 figs..