Redescription of Squalus acutipinnis Regan, 1908, a Valid Species of Spiny Dogfish from Southern Africa (Chondrichthyes: Squaliformes: Squalidae)

The Bluntnose spiny dogfish Squalus acutipinnis Regan, 1908 is redescribed based on the re-examination of its type specimens and non-type material from Southern Africa. The taxonomic confusion concerning its validity is mainly related to its heterogeneous type series. Its taxonomic status is clarified as a valid species endemic to the Southwestern Indian Ocean when compared to congeners from the region and other valid species with which it has been placed in synonymy. Squalus acutipinnis can be distinguished from all species of the “megalops-cubensis group” by fewer total, precaudal, and monospondylous vertebrae (except from Squalus megalops, Squalus brevirostris, and Squalus crassispinus). Squalus acutipinnis is clearly distinct from Squalus megalops from Southern Australia and the Japanese S. brevirostris through characters of pectoral fin and external measurements. The South African species differs from S. crassispinus by having more slender first and second dorsal-fin spines. Squalus acutipinnis is also easily distinguished from the regional congeners S. acanthias, S. blainvillei, and S. mitsukurii by having lanceolate dermal denticles (vs. non-lanceolate unicuspid denticles in S. acanthias, and non-lanceolate tricuspid denticles in S. blainvillei and S. mitsukurii).