Aotearorchestia, 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 : 6-7

Aotearorchestia gen. nov.

Type species. Talorchestia telluris Spence Bate, 1862 , original designation.

Included species. Aotearorchestia includes 2 species: A. chathamensis ( Hurley, 1956) and A. telluris ( Spence Bate, 1862) .

Category. Mascupod ( Lowry & Myers 2019).

Habitat. Sand-hopper ( Lowry & Myers 2019).

Etymology. From Aotearoa, the Maori name for New Zealand plus the stem Orchestia , gender feminine.

Diagnostic description. Eye medium (1/5–1/3 head length). Antenna 1 long, reaching to at least midpoint of peduncular article 5 of antenna 2. Antenna 2 peduncular articles slender; article 3 without plate or process ventrally. Mandible left lacinia mobilis 4-cuspidate. Maxilliped outer margin of precoxa not stepped; palp slender, or broad; palp article 2 with distomedial lobe; article 4 fused with article 3. 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 5 groups of robust setae, propodus ‘subtriangular’ with well-developed posterodistal lobe, palm transverse. Gnathopod 2 subchelate; posterior margin of merus, carpus and propodus each without lobe covered in palmate setae; propodus palm acute; dactylus not modified distally, blunt, shorter than posterior margin of propodus or longer than posterior margin of propodus. Pereopods 3–7 simplidactylate or bicuspidactylate. Pereopod 5 short, less than 2/3 length of pereopod 6, or long, more than 2/3 length of pereopod 6; merus broad, longer than broad, expanded distally; dactylus long, slender, not inflated. Pereopod 6 not sexually dimorphic; basis expanded. Pereopods 6–7 without row of short setae along posterior margin of dactyli. Pereopod 7 sexually dimorphic; basis expanded, merus moderately expanded, carpus massive, plate-like; male basis not expanded into plate-like structure; basis expanded; merus expanded; carpus with massive plate-like expansion. Pleonites 1–3 without dorsal spines. Pleopods 1–3 all well-developed, non-segmented. Epimera 1–3 slits absent. Uropod 1 peduncle distolateral robust seta absent; male exopod not sexually dimorphic, with marginal setae in one row. 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 1 or 2 rows. Uropod 2 exopod with marginal robust setae in 1 or 2 rows; endopod with marginal robust setae in 2 rows. Uropod 3 ramus subequal in length to peduncle. Telson as broad as long, rounded distally, apically incised (weakly), complete dorsal ridge or dorsal groove to at least half the length, with apical and marginal robust setae, with at least 10 robust setae per lobe.

Remarks. Serejo & Lowry (2008) placed Talorchestia chathamensis Hurley, 1956 in their newly established genus Bellorchestia , but overlooked transferring its closely aligned sister taxon T. telluris ( Spence Bate, 1862) . Both Aotearorchestia and Bellorchestia have robust setae on the upper lip, along with Hermesorchestia Hughes & Lowry, 2017 . The extreme dimorphism in the male pereopods separates Aotearorchestia and Hermesorchestia from Bellorchestia .

Aotearorchestia gen. nov., along with Africorchestia Lowry & Coleman, 2011 , Gondwanorchestia Lowry, Myers & Perez-Schultheiss, 2020 and Hermesorchestia Hughes & Lowry, 2017 are typified by extreme sexual dimorphism in pereopods 6 and 7 of adult males ( Fig. 68 ). Aotearorchestia gen. nov. is distinguished by the expanded carpus of pereopod 7 which forms a plate-like structure, while in Hermesorchestia and Gondwanorchestia it is the basis which is expanded into a laminar plate-like structure. In species of Africorchestia the pereopodal dimorphism is expressed as an extreme elongation of the pereopods.

Distribution. New Zealand.

Figures

FIGURE 68. Fieldguide to New Zealand Coastal Talitrids Subantarctorchestia aucklandiae (Spence Bate, 1862) gen. et comb. nov., Subantarctorchestia bollonsi (Chilton, 1909) gen. et comb. nov., Bellorchestia spadix (Hurley, 1956), Tatahipeke cookii gen. et. comb. nov., T. tumida (Stebbing, 1887) gen. et comb nov. (Part 2 of 3).