Author: Bocage and Capello, 1864
Field Marks:
Dark colour, without conspicuous fin markings, no anal fin, small fin spines on both dorsals, moderately long snout, slender-cusped teeth without cusplets in upper jaw, bladelike, erect or semi-erect, largecusped interlocked cutting teeth in lower jaw, pectoral fins with broadly rounded free rear tips, no keels on caudal peduncle.
Diagnostic Features:
Anterior nasal flaps short, not expanded into barbels; snout moderately long, pointed and flattened, length about 2/5 of head length and 2/5 to 2/3 of distance from mouth to pectoral origins; gill openings moderately wide, last one slightly wider or narrower than first four; lips thin, not fringed, pleated or suctorial; teeth strongly different in upper and lower jaws, uppers small, with very narrow, acute, erect cusps and no cusplets, not bladelike, lowers much larger, bladelike, interlocked, with a high, broad, erect or semierect cusp and distal blade, edges not serrated; tooth rows 57 to 59/31 to 33. Dorsal fins with small, somewhat inconspicuous, grooved spines, the second dorsal spine not markedly larger than the first; first dorsal somewhat posterior on back, origin over or well posterior to pectoral inner margins, insertion well anterior to pelvic origins but varying from slightly closer to the pelvic bases than the pectorals to vice versa; second dorsal slightly larger than first but with base less than 1.5 times as long as first; origin of second dorsal fin over about middle third of pelvic bases; pectoral fins with short, broadly rounded free rear tips and inner margins not expanded and acute or lobate; caudal fin asymmetrical, not paddle-shaped, with a long upper lobe, short to poorly differentiated lower lobe, and with subterminal notch varying from virtually absent to well-differentiated. No precaudal pits, lateral or midventral keels on caudal peduncle. Dermal denticles with moderately high, narrow pedicels and broad, flat leaf-shaped, tricusped and triridged crowns. Colour blackish brown or dark brown, without conspicuous fin markings.
Remarks:
See Remarks above for the genus Centroscymnus for a discussion of the separation of that genus from Scymnodon. Zameus was proposed by Jordan and Fowler (1903) for S. squamulosus, a species very closely allied to the Atlantic S. obscurus but morphologically divergent from the type of Scymnodon, S. ringens. Zameus could be used to separate S. obscurus and S. squamulosus at the subgeneric or generic level if necessary. Garman (1913); Fowler (1941) and Garrick (1959b) all included Centrophorus plunketi Waite, 1909 in Scymnodon on denticle characters, but I follow Bigelow and Schroeder (1957) in placing it in Centroscymnus in as much as its teeth are closer to the Centroscymnus end of the Centroscymnus-Scymnodon continuum.