A new species of deep-sea catshark (Sycliorhinidae: Bythaelurus) from the southwestern Indian Ocean
Bythaelurus naylori sp. n. is described based on 41 specimens collected from seamounts in the southwestern Indian Ocean. The new species can be separated from all other Bythaelurus species by a combination of distinctly enlarged dermal denticles on the upper caudal-fin margin, lack of papillae on the roof of the mouth and tongue, an anal-fin base length equal to or less than 1.5 times second dorsal-fin base length, and a uniformly plain medium to dark brown body coloration, with light fin edges and a distinct dark dusky-colored snout. No other Bythaelurus species has the combination of a caudal crest of prominent, distinctly enlarged, comb-like dermal denticles along the upper caudal margin and lacks oral papillae. Bythaelurus naylori sp. n. can be distinguished from its two closest cogeners, B. giddingsi and B. lutarius, by a combindation of prominent comb-like dermal denticles along the upper caudal-fin margin, absence of oral papillae, uniform body coloration, and noticeable dark dusky snouth; Bythaelurus giddingsi has oral papillae present and a variegated color pattern, while B. lutarius lacks a caudal crest of enlarged denticles and matures at a much smaller size than the new species.