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Author: Teng, 1962

Hexanchus nakamurai Teng, 1962

Diagnosis: similar to H. griseus but head less broad, snout longer and pointed; also, anterior cusp of teeth much larger, especially in upper jaw, upper front 4 rows of teeth in advance of line formed by lateral teeth, lower lateral teeth in 5 rows. Gill-slits 6. Spineless dorsal fin more advanced, mostly before anal fin base; pectoral fins with somewhat concave posterior margin; lower caudal lobe distinct. Colour: plain grey, slightly darker dorsally. Size: to about 1.8 m TL.

Habitat: probably mesopelagic to benthic in deeper waters (recorded from 90 to 350 m), possibly with excursions to surface or shallows; in warmer seas than H. griseus. Food: only fish recorded. Reproduction: ovoviviparous, litters of up to 26 embryos known; about 40-45 cm at birth.

Distribution: occurs in warmer waters of Clofnam area, where possibly confused with H. griseus (which it probably replaces). Elsewhere, Florida, Gulf of Mexico, Caribbean area, southern Atlantic, south-western Indian Ocean (Natal to Kenia) and Taiwan.

Note: the availability of Teng's paper for nomenclatural purposes has been considered by recent authors (Compagno, 1984; Taniuchi & Tachikawa, 1991; Tortonese, 1985; also Boeseman 1984:[1427]), without reaching unanimity. If further evidence proves the name nakamura to be invalid, the name H. vitulus Springer & Waller, employed by most recent authors, should be retained.

Eggs, larvae and young stages. Springer & Waller, 1969: 1671 Bigelow & Schroeder, 1948, fig. 9A (cf. Springer & Waller, loc. cit.).

Bigeyed six-gill shark (Hexanchus nakamurai)