Sympenchelys, Hibino, Yusuke, Ho, Hsuan-Ching & Kimura, Seishi, 2015

Hibino, Yusuke, Ho, Hsuan-Ching & Kimura, Seishi, 2015, A new genus and species of worm eels, Sympenchelys taiwanensis (Anguilliformes: Ophichthidae: Myrophinae), from the northwestern Pacific Ocean, Zootaxa 4060 (1), pp. 41-48 : 42-43

Sympenchelys gen. nov.

Type species. Sympenchelys taiwanensis sp. nov.

Diagnosis. A genus of the family Ophichthidae , subfamily Myrophinae , defined by neural and haemal spines with well-developed paddle-like tips ( Fig. 1 ) and the following combination of characters: anterior nostril tubular; posterior nostril opening outside of mouth, above upper lip, with a short flap anteriorly; eye located above anterior half of upper jaw; teeth on jaws, vomer and intermaxillary region, generally large, recurved and pointed; a single sensory pore located between anterior and posterior nostrils; three preopercular pores; gill opening large, not constricted; pectoral fin absent, but an extremely short dermal flap located just after gill opening; maxilla relatively slender and distinctly tapered posteriorly; supraoccipital crest not developed.

Description. Body long, extremely compressed laterally, preanal length shorter than tail ( Fig. 2 ). Anterior nostril tubular; posterior nostril opening outside of mouth, above upper lip, with a short flap anteriorly; eye located above anterior half of upper jaw; mouth inferior; mouth large; lips smooth. Teeth on jaws, vomer and intermaxillary region, generally large, recurved and pointed. Gill opening large, not constricted; an extremely short dermal flap located just after gill opening. Median fins low, confluent with caudal fin; origin of dorsal fin located before anus. Sensory pores of head developed, supraorbital, infraorbital, preoperculomandibular, interorbital and supratemporal pores present. Gill arches less developed: first basibranchial ossified, second to fourth basibranchials cartilaginous; first and second hypobranchials ossified, third cartilaginous; first to fourth ceratobranchials ossified, fifth absent; first to fourth epibranchials ossified; first and second interbranchials ossified; third upper pharyngeal tooth plate with three conical teeth, fourth upper pharyngeal tooth plate with 16 conical teeth arranged as an oval ring along edge of plate and scattered inside, both plates closely sutured but not fused; lower pharyngeal tooth plate with 15 conical teeth in two longitudinal rows. Jaws elongate; maxillae relatively slender and distinctly tapered posteriorly. Eight branchiostegal rays attached to each epihyal with 31 unattached pairs well behind basal arch. Pectoral girdle reduced to extremely slender cleithrum and supracleithum. Supraoccipital crest not developed. Epipleural ribs on all precaudal vertebrae. Neural and haemal spines with welldeveloped paddle-like tips.

Etymology. The scientific name is derived from its compressed body and neural and haemal spines, the Greek sympiez (compress) and enchelys (an eel), feminine.

Remarks. The genus can be distinguished from all other myrophine genera by the well-developed neural and haemal spines with paddle-like tips. Although Muraenichthys gymnopterus (Bleeker 1853) and Muraenichthys thompsoni Jordan & Richardson 1908 have relatively better developed neural and haemal spines, their neural spines have pointed, not paddle-shaped tips.

Sympenchelys is also easily distinguished from eight ( Ahlia Jordan & Davis 1891, Asarcenchelys McCosker 1985 , Benthenchelys Fowler 1934 , Mixomyrophis McCosker 1985 , Myrophis Lütken 1852 , Neenchelys Bamber 1915 , Pseudomyrophis Wade 1946 , Pylorobranchus McCosker & Chen 2012 ) of 14 genera of Myrophinae by the absence of its pectoral fin. The genus differs from other genera lacking pectoral-fins ( Glenoglossa McCosker 1982 , Schultzidia Gosline 1951 , Schismorhynchus McCosker 1970 , and Scolecenchelys Ogilby 1897 ) in the position of the posterior nostril (outside of mouth in Sympenchelys vs. within or along upper lip), the position of the eye (anterior to mid jaw vs. posterior to mid jaw except Glenoglossa ), and the presence of vomerine teeth (present vs. absent in Glenoglossa and Schultzidia ).

The genus resembles Muraenichthys Bleeker 1853 and Skythrenchelys Castle & McCosker 1999 in the position of the posterior nostril and the eye. However, the former can be distinguished from the latter two genera by having an unconstricted gill opening (vs. constricted in Muraenichthys ), a minute flap just posterior to the gill opening (vs. absent in Skythrenchelys ), a slender cleithrum (vs. stout in Skythrenchelys ), three preopercular pores (vs. two in Skythrenchelys ), a slender and distinctly tapered maxilla (vs. stout and weakly tapered in Skythrenchelys ), an undeveloped supraoccipital crest (vs. developed in Muraenichthys ), and large and recurved teeth on jaws and vomer (vs. blunt or pointed but small conical teeth in Muraenichthys ).

Sympenchelys has an extremely minute flap just after the gill opening ( Fig. 3 ). Although its shape is similar to a small pectoral fin, it is not regarded as a pectoral fin because of the much reduced elements of the pectoral girdle, absence of fin-rays, the strange position of the flap compared with other Myrophinae , and a vertical membrane connected with the flap from both vertical sides.

Figures

FIGURE 1. Caudal vertebrae of Sympenchelys taiwanensis sp. nov. a NMMB-P 17554, paratype, 194.0 mm TL (cleared-and-stained); b ASIZP 60198, paratype, 279.0 mm TL (soft-X ray photograph).

FIGURE 2. Fresh condition of Sympenchelys taiwanensis sp. nov., NMMB-P 22188, holotype, 258.8 mm TL, collected from Donggang, Taiwan. A, position of anus; D, origin of dorsal fin.

FIGURE 3. Magnification around left gill opening of Sympenchelys taiwanensis sp. nov., ASIZP 60198, paratype, 279.0 mm TL. Arrow indicates an extremely short dermal flap.