Aristias Boeck, 1871: 106. — Stebbing, 1906: 49. — Hurley, 1963: 40, 41 (key). —J.L. Barnard, 1969: 324. — Lincoln, 1979: 60. — Barnard & Karaman, 1991: 465. — Lowry & Stoddart, 1997: 14.
Type species. Anonyx tumidus Krøyer, 1846, by monotypy.
Diagnosis (modified after Lowry & Stoddart 1997). Head deeper than long. Epistome and upper lip fused. Mandibles usually asymmetrical, left straight, minutely serrate, right straight or slightly convex, smooth; left lacinia mobilis minute or absent; accessory setal row well developed or absent, if present with more than 5 accessory setae; molar a small, weakly setose flap or absent. Maxilla 1 inner plate strongly setose, usually with more than 2 pappose setae, outer plate broad, setal teeth in a modified 7/4 arrangement; palp 2-articulate. Maxilliped outer plate without apical robust setae; palp well-developed, 4-articulate. Gnathopod 1 simple to parachelate, coxa vestigial, posterior margin of propodus serrate. Gnathopod 2 coxa well developed. Pereopods 3–7 simple, propodus usually with a distal spur. Pereopod 4 deeper than wide with weak posteroventral lobe. Pereopod 5 coxa with well-developed posteroventral lobe. Gills from gnathopod 2 to pereopod 6, not pleated. Telson moderately to deeply cleft.
Species composition and distributions. Aristias includes 28 species worldwide. Antarctic and sub- Antarctic: A. antarcticus Walker, 1906 (Cape Adare; Commonwealth Bay; Davis Sea, Kerguelen Islands; Magellan area; Ross Sea; South Georgia; South Shetland Islands; Weddell Sea); A. collinus K.H. Barnard, 1932 (South Shetland Islands; Weddell Sea); A. excavatus sp. nov. (Ross Sea). Atlantic Ocean and Arctic: A. bicornuta Ortiz, Lalana & Varela, 2007 (Cuba); A. captiva Lowry & Stoddart, 1997 (Gulf of Mexico); A. commensalis Bonnier, 1896 (Bay of Biscay); A. falcatus Stephensen, 1923 (S.W. of the Faeroe Islands); A. megalops G.O. Sars, 1895 (Norway); A. microps G.O. Sars, 1895 (Norway); A. neglectus Hansen, 1888 (widespread along European coasts from the Adriatic to Norway); A. topsenti Chevreux, 1900 (Newfoundland); A. tumidus (Krøyer, 1846) (Arctic Ocean). Indian Ocean: A. madagascarensis Ledoyer, 1972 (Madagascar); A. stenopodus Ledoyer, 1986 (Madagascar); A. symbioticus K.H. Barnard, 1916 (South Africa; Madagascar). Pacific Ocean: A. adrogans J.L. Barnard, 1964 (Alaska); A. coriolis Lowry & Stoddart, 1993 (Philippines); A. curtipes Gurjanova, 1962 (Pacific Ocean, west of Japan); A. expers J.L. Barnard, 1967 (Baja California); A. japonicus Gurjanova, 1962 (Sea of Japan); A. nonspinus Hirayama, 1985 (Japan); A. pacificus Schellenberg, 1936 (Japan; Vancouver Island); A. spinipes Gurjanova, 1962 (east of Kamchatka Peninsula); A. thio Lowry & Stoddart, 1994 (New Caledonia); A. tropicus Schellenberg, 1938 (Bismarck Archipelago, Papua New Guinea); A. uokonia Lowry & Stoddart, 1994 (New Caledonia); A. veleronis Hurley, 1963 (Puget Sound); A. verdensis Lowry & Stoddart, 1993 (Philippines).
Known fauna associations. A. excavatus sp. nov. is associated with the sponge Myxodoryx hanitschi; A. bicornuta associated with the hexactinellid sponge Lefroyella crispa; A. commensalis associated with a sponge and an asteroid; A. neglectus recorded associations include the brachiopod Terebratulina caputserpentis, the anemone Bolocera tuediae, sponges Geodia spp., and ascidians; A. topsenti, associated with a species of sponge; A. tumidus, associated with the tunicate Molgula retortiformis; A. symbioticus, associated with an ophiuroid and a sponge; A. pacificus, associated with the ascidian Ascidia paratropa.