Subantarctorchestia, Hughes & Lowry, 2023

Hughes, Lauren E. & Lowry, James K., 2023, Review of New Zealand Coastal Talitroids with description of three new genera (Crustacea, Amphipoda, Senticaudata), Zootaxa 5268 (1), pp. 1-81 : 35

Subantarctorchestia gen. nov.

Type species. Orchestia aucklandiae Spence Bate, 1862 , original designation.

Included species. Subantarctorchestia includes 2 species, S. aucklandiae ( Spence Bate, 1862) ; S. bollonsi ( Chilton, 1909) .

Category. Mascupod.

Habitat. Beach-hopper (habitat for S. bollonsi suspect according to Hurley (1957)).

Etymology. Named for the Subantarctic, the environment in which it lives plus the stem Orchestia .

Diagnostic description. Eye medium (1/5–1/3 head length). Antenna 1 short, not reaching midpoint of peduncular article 5 of antenna 2. Antenna 2 peduncular articles slightly to strongly incrassate; article 3 without plate or process ventrally. Maxilliped palp broad; article 2 with distomedial lobe; article 4 reduced, button-shaped. Pereonites without transverse ridges, or with transverse ridges. Gnathopod 1 sexually dimorphic; subchelate; posterior margin of carpus and propodus each with lobe covered in palmate setae; carpus longer than propodus; propodus anterior margin with 6 or 7 groups of robust setae, propodus ‘subtriangular’ with welldeveloped posterodistal lobe, palm transverse. Gnathopod 2 subchelate; posterior margin of merus, carpus and propodus each without lobe covered in palmate setae; propodus palm acute; without proximal sinus; with broad sinus near dactylar hinge; without proximal spine defining palm; dactylus not modified distally, blunt, shorter than posterior margin of propodus. Oostegites setae with simple smooth tips. Pereopods 3–7 bicuspidactylate. Pereopod 6 not sexually dimorphic; basis expanded. Pereopod 7 not sexually dimorphic; basis posterodistal lobe extending to merus; basis, merus, and carpus 3-dimensional, not laminar, male basis not expanded into plate-like structure; basis expanded. Pleonites 1–3 without dorsal spines. Pleopods 1–3 all well-developed. Epimera 1–3 slits absent. Uropod 1 male exopod not sexually dimorphic, peduncle distolateral robust seta present, with simple tip. Uropods 1–2 rami without apical spear-shaped setae. Uropod 1 endopod with marginal robust setae in 2 rows; exopod with marginal robust setae in one row. Uropod 2 exopod with marginal robust setae in 1 row; endopod with marginal robust setae in 2 rows. Uropod 3 ramus linear (narrowing); longer than peduncle. Telson longer than broad, tapering distally, apically incised, apical dorsal groove, with apical and marginal robust setae, with 7–9 robust setae per lobe.

Remarks. Subantarctorchestia shares a number of important generic-level characters with Orchestia including the slender antenna 2. They differ mainly in the structure of gnathopod 2 and pereopod 7. The gnathopod 2 is without proximal setae on the gnathopod 2 palm Orchestia , present in Subantarctorchestia ) and pereopod 7 (sexually dimorphic in Orchestia , not sexually dimorphic in Subantarctorchestia ).

Distribution. New Zealand. Campbell Island, Auckland Islands, Stewart Island, South Island, ( Spence Bate 1862; Chilton 1909; Hurley 1957).