Two new species of short-snouted dogfish sharks of the genus Squalus Linnaeus, 1758, from southern Africa (Chondrichthyes: Squaliformes: Squalidae)

Abstract

Species composition of the genus Squalus from the eastern Atlantic and western Indian oceans is still poorly known, with three to four species often recognized: S. acanthias, S. megalops, S. blainvillei, and S. mitsukurii. A fifth species, S. acutipinnis, was recently redescribed as valid in the region, although morphological variation was noted among its type specimens that indicated the presence of two different forms. The second form is described herein as Squalus margaretsmithae sp. nov. and distinguished from S. acutipinnis based on external morphological characters. Squalus mahia sp. nov. is also described from southern Africa based mostly on material collected from Madagascar. Squalus mahia sp. nov. stands out from other Squalus species by having a conspicuously slender body, elongate and thin dorsal fin spines, narrow caudal fin, and other external proportions. These two species are often misidentified with the Australian S. megalops because they share a short snout, white postventral caudal margins, lanceolate and unicuspid dermal denticles, and a low number of vertebrae. Comparative analyses are provided here between Squalus margaretsmithae sp. nov., Squalus mahia sp. nov., and morphologically similar species that also share these features, including S. brevirostris, S. crassispinus, S. acutipinnis, S. altipinnis, and S. hemipinnis. A taxonomic evaluation of the nominal species S. megalops and its occurrence in the region is also discussed.