Insularorchestia, Lowry & Myers, 2022

Lowry, J. K. & Myers, A. A., 2022, Platorchestiinae subfam. nov. (Amphipoda, Senticaudata, Talitridae) with the description of three new genera and four new species, Zootaxa 5100 (1), pp. 1-53 : 17-19

Insularorchestia gen. nov.

Type species. Orchestia ashmoleorum Stock, 1996 , current designation.

Included species. Insularorchestia includes 3 species: I. ashmoleorum ( Stock, 1996) com. nov.; I. monodi (Mateus, Mateus & Afonso, 1986) com. nov. and I. susorum sp. nov. of Stock & Biernbaum, 1994 com. nov..

Ecological type. Beach-hoppers, field-hoppers.

Habitat. Sand beaches and under stones at 762 m altitude ( Stock & Biernbaum 1994).

Etymology. From islands.

Diagnostic description (male). Based on Mateus, Mateus & Afonso (1986), Stock (1996), Serejo (2004), Morino & Ortal (1995) and Stock & Biernbaum (1994).

Head. Antenna 2 peduncular articles incrassate. Mandible left lacinia mobilis 5- or 6-cuspidate. Labium without inner lobes, with possible vestigial inner lobes. Maxilliped palp article 2 with distomedial lobe; article 4 reduced, button-shaped or fused with article 3.

Pereon. Gnathopod 1 sexually dimorphic; subchelate; coxa much smaller that coxa 2; posterior margin of carpus and propodus each with lobe covered in palmate setae; propodus anterior margin with 3 or 4 groups of robust setae, subrectangular or ‘subtriangular’ with well-developed posterodistal lobe, palm transverse; dactylus simplidactylate. Gnathopod 2 subchelate; propodus palm acute, evenly rounded or irregular with small to large shallow midpalmar sinus or without distal palmar sinus; with or without proximal spine or thumb defining palm; dactylus not modified distally, blunt or short, recurved distally or attenuated distally. Pereopods 3–7 dactyli bicuspidactylate. Pereopod 4 significantly shorter than pereopod 3 or subequal or slightly shorter than pereopod 3; carpus similar in length to that of pereopod 3 or significantly shorter than that of pereopod 3; dactylus amplidactylate, thickened proximally with notch midway along posterior margin or short, thickened. Pereopod 6 subequal in length to pereopod 7, not incrassate; basis moderately expanded; male merus and carpus not expanded or male merus expanded, carpus not expanded. Pereopod 7 not incrassate; basis broadly expanded; posterior margin with distinct minute serrations, each with a small seta, posterodistal lobe present or posterodistal lobe absent, shallow, broadly rounded; merus expanded distally, subtriangular, anterior margin slightly convex; carpus unexpanded or expanded, subrectangular, subequal to or shorter than propodus; propodus broad or propodus slender; length 4.7–7.3 × width; propodus without large distal tuft of setae. Oostegites (female) setae with simple smooth tips.

Pleon. Pleopods 1–3 all well-developed. Uropod 1 peduncle distolateral robust seta absent; exopod without marginal robust setae; endopod with marginal robust setae in 2 rows. Uropod 2 exopod with marginal robust setae in 1 row; endopod with marginal robust setae in 2 rows. Uropod 3 ramus subequal in length to peduncle, or shorter than peduncle. Telson apically incised, with 3–6 robust setae per lobe.

Remarks. Insularorchestia is most similar to Platorchestia . It differs in having a simplidactylate gnathopod 1 (cuspidactylate in Platorchestia ).

Distribution. South Atlantic Ocean. Saint Helena ( Stock 1996); Ascension Island ( Stock & Biernbaum 1994). North Atlantic Ocean. Azores (Mateus, Mateus & Afonso 1986).