Pleuroprion

Genus Pleuroprion zur Strassen, 1903

Antares zur Strassen, 1902: 687–688 (preoccupied).

Pleuroprion.—zur Strassen, 1903: 31 (replacement name).— Richardson, 1905: 342, key to species.— Stebbing 1908: 51–52.— Barnard, 1914: 216.— Hansen, 1916: 193–194, key to species.— Gurjanova, 1933: 160.— Gurjanova, 1936: 197–198, key to species.— Kensley, 1978: 33.— Kussakin, 1982: 420–421, key to species.— Wägele, 1989: 138–139.— Poore, 2001: 224.— Poore, 2015: 14.

Diagnosis: Body flattened, with subparallel pereonites, pereonite 1 separated from head by shallow transverse groove, lateral margins of head and pereonite 1 shallow, convex. Pleonite 1 articulating with pleotelson, its posterior dorsal margin clearly indicated. Pleonite 2 of male dorsally doomed. Eyes prominent, bulbous. Antenna 2 flagellum of 2 articles plus claw. Maxillipedal palp article 3 not mesially lobed, about 1.5 times as wide as article 4. Pereopod 1 dactylus with unguis. Pereopods 2–4 with carpus longer than ischium and merus together; carpus and propodus tapering; fringed with long, pappose setae and some single simple setae on inferior margin; dactylus slender, unguis less than half length of body of dactylus, total 0.6 times propodus. Uropod biramous; exopod with terminal robust seta; endopod shorter than wide, with terminal stout seta. Penial plate tapering, apically bifid. Pleopod 1 of male exopod with 13 lateral plumose setae, with 9 distomesial plumose setae, with strong groove on its posterior face opening on short distolateral lobe; endopod shorter than exopod. Pleopod 2 with styliform appendix masculina, slightly longer than endopod. Oostegites unknown.

Type species: Antares chuni zur Strassen, 1902.

Included species: Pleuroprion chuni (zur Strassen, 1902).

Remarks: Zur Strassen (1902) described a new species collected off South Africa and placed it in a new genus Antares. However, Antares was preoccupided and zur Strassen (1903) replaced it with Pleuroprion zur Strassen, 1903. Zur Strassen (1902, 1903) did not provide a generic diagnosis but distinguished it from Antarcturus zur Strassen, 1902, by the shape and spination of the head, size, shape and fusion of the first pereonite with the head without a clear suture, the epimera not distinct from the pereonites, and pleonite 1 articulating with the pleotelson. He noticed the difference in the shape of the fourth pereonite between Pleuroprion and other „arcturids“ s.l., and found the body of Pleuroprion to be more asellote-like than arcturid-like.

Richardson (1905) provided a short diagnosis of Pleuroprion without consulting type material and added no detail. She included two species, Arcturus murdochi Benedict, 1898, and A. intermedius Richardson, 1899a, without discussion. Hansen (1916) found Pleuroprion closely allied to Arcturus Latreille, 1829, and moved Arcturus hystrix G.O. Sars, 1877, to Pleuroprion and described a new species, Pleuroprion frigidum Hansen, 1916. Neither author discussed Pleuroprion chuni. Kussakin (1982) found Pleuroprion intermediate between Neastacilla Tattersall, 1921, and Idarcturus Barnard, 1914b, though by some characters being close to Arcturus.

Wägele (1989) suggested that Pleuroprion (as then diagnosed) belonged to an early branch of Arcturinae (now partly Antarcturidae), since their body was similar to those of the Pseudidotheinae. Wägele (1989) stated that isopod does not geniculate between pereonites 4 and 5. The simple, undifferentiated ungues of the pereopods would also support the suggestion of Wägele (1989) that these are primitive antarcturids. Later, Poore (2001) placed the genus within Antarcturidae.

Pleuroprion, as now defined and containing only the type species, Pleuroprion chuni, is clearly a member of Holidoteidae, possessing a body without geniculation between pereonites 4 and 5, an apically bifid and splayed penial plate, both uropodal rami with a robust terminal seta and the uropodal exopod shorter than wide. Pleuroprion resembles Austroarcturus and differs from the other genera, Neoarcturus and Holidotea, in having a suture between the first and second pleonites and in having pereopods 2–4 fringed with dense pappose setae along the posterior margin.

Pleuroprion differs from Holidotea and Austroarcturus in the narrower maxilliped palp, shorter terminal grooved lobe of the male pleopod 1 endopod, in ratio of the lengths of the rami of male pleopod 1, and in the relatively longer appendix masculina. Pleuroprion differs from Neoarcturus in having tergites of pereonite 1 to pleotelson well developed, the posterior ventral margin of pereonite 4 not notched in the male, by having several setae along pereopods 2–4 carpus and propodus and the ungues of pereopods 2–4 being shorter than the body of dactylus.