Abstract
A new acanthaspidiid species, Acanthaspidia matsi sp. nov., is described from the Powell Basin slope (Weddell Sea, Southern Ocean). Specimens of the new species were collected during the expedition ANDEEP III on board RV Polarstern in March 2005. The new species most closely resembles Acanthaspidia typhlops (G. O. Sars, 1879), Acanthaspidia natalensis (Kensley, 1977) andAcanthaspidia bifurcatoides Kussakin & Vasina, 1982, but can be distinguished from all these species by the following characters: rostrum strongly trifid (tips 0.4 times rostrum length); pereonites 1, 3–4 and 6 with 2 mid-dorsal spines; pleotelson spinulated, with 2 robust mid-dorsal spines. Systematic difficulties to distinguish the genera Acanthaspidia Stebbing, 1898 and Ianthopsis Beddard, 1886 are discussed and a key to all species in the genus Acanthaspidia is provided.