Common Name
Nielsen's Assfish
Year Described
Tomiyama, Takami & Fukui, 2018
Identification
Dorsal Fin: 122-129
Anal Fin: 101-109
Pelvic Fin: 1
Pectoral Fin: 24-29
Caudal Fin: 7-9
Gill Rakers: 11-14 (long rakers on first arch)
Vertebrae: 13-14 (precaudal), 54-58 (caudal), 67-71 (total)
Oblique Scales: 20-25
Body elongate, compressed, and tapering strongly post-anus. Body depth 8-15% SL. Head large (HL 18-21% SL). Mouth inferior. Anterior nostril on snout, posterior between front nostril and eye. Eye small. Mouth large, extending well past orbit. Rear of maxilla expanded. Tooth patches present on dentary, vomer, palatine, and basibranchial (one median patch). Teeth tiny and conical. Preopercle lacks spines. Opercular spine weak. Dorsal and anal fins continuous with tail. Dorsal fin origin between preopercle and pectoral base (predorsal length 16-20% SL). Anal fin base averages under the 24th dorsal fin ray. Dorsal fin slightly higher anteriorly. Caudal fin present but small. Pectoral fin moderate, at eye level, and fan-like. Pelvic fin origin anterior to preopercle and not reaching anus. Body flabby and weakly muscled. Cycloid scales cover head and body but absent on jaw. Lateral line absent.
Color
Color dark brown in preservative with paler yellow-brown fins. Gill area and peritoneum blackish.
Size
Specimens range from 147-615mm SL.
Habitat
Abyssal over soft bottoms (3155-5440m).
Range
Known from the Sargasso Sea area south of Bermuda, the eastern Caribbean, and the Gulf of Mexico. Also in the northeastern Atlantic.
References
Tomiyama, S., M. Takami, and A. Fukui. 2018. A new deepwater assfish, Bassozetus nielseni sp. nov.(Ophidiiformes: Ophidiidae), from the North Atlantic and West Indian oceans. Ichthyological Research, 65, 353-362.
Other Notes
Records of Bassozetus compressus and B. elongatus in the Atlantic refer to this species.