Sciadonus robinsi, Nielsen, 2018

Nielsen, Jørgen G., 2018, Revision of the cosmopolitan deep-sea genus Sciadonus (Teleostei, Bythitidae) with two new species, Cybium 42 (2), pp. 177-187 : 185

Sciadonus robinsi n. sp.

( Tab. I, Figs 1 , 14 )

Material examined (1 specimen, SL 47 mm)

Holotype. UF 187413 , SL 47 mm, male, off northeastern Brazil, 1°58’N, 40°54’W, R / V Gillis , st. 77, 41’semi-balloon otter trawl, 4416-4422 m, 10 Aug. 1973.

Diagnosis

Sciadonus robinsi is long, slender and compressed. Mouth horizontal. No tissue flaps anteriorly on protruding lower jaw. No black pigment spots seen through transparent skin. Dorsal fin with 81 rays, anal fin with 53 rays, pectoral fin with 14 rays and pelvic fins absent. Precaudal vertebrae 37 and total vertebrae 77. Predorsal length 42.5% SL.

Description

The principal meristic and morphometric characters are shown in table I. Body slender and compressed with loose, scaleless skin. Inner organs seen through transparent skin ( Fig. 14 ). Mouth horizontal with protruding lower jaw. Tiny deep-set, black eyes placed above a point just posterior to end of upper jaw. Opercular spine absent. Otolith dissolved. Origin of dorsal fin shortly behind tip of pectoral fin and origin of anal fin well behind midpoint of fish. Vertical fins joined. Pectoral peduncle three times as long as high. Pelvic fins absent. Anterior gill arch with 12 tiny rakers and small filaments. Second and third arches with rakers and filaments somewhat larger. Pseudobranchial filaments not observed. A well-developed urogenital hood covering a small penis. Proximal half of hood with a wing-like extension on each side. Length of distinct testes 11 mm.

Figures

Figure 1. – Records of Sciadonus species.

Figure 14. – Sciadonus robinsi n. sp.: UF 187413, holotype, male, SL 47 mm. (Photo after 42 years of preservation).