Pseudorchestoidea Bousfield, 1982

Bopiah, Arundathi, 2012, Britorchestia, a new talitrid genus from western Europe and the Mediterranean Sea and a revision of Pseudorchestoidea and Sardorchestia (Crustacea, Amphipoda, Talitridae), Zootaxa 3451, pp. 60-67 : 64-65

Pseudorchestoidea Bousfield, 1982

Orchestoidea .— Bulycheva, 1957: 130 (in part).— J.L. Barnard, 1969: 471 (in part). Pseudorchestoidea Bousfield, 1982: 47 .

Type species. Orchestia biolleyi Stebbing, 1908 , original designation.

Included species. Pseudorchestoidea includes 3 species: P. biolleyi ( Stebbing, 1908) ; P. meridionalis ( Schuster, 1954) ; P. mexicana Bousfield, 1982 .

Diagnostic description (based on male). Eyes large (greater than 1/3 head length). Antenna 1 short, not longer than article 4 of antenna 2 peduncle. Antenna 2 peduncular articles slender; peduncular article 3 without ventral process. Labrum without robust setae. Mandible left lacinia mobilis 4 or 5-dentate. Maxilliped palp article 2 distomedial lobe well developed; article 4 fused to article 3. Gnathopod 1 parachelate; posterior margin of carpus and propodus each with lobe covered in palmate setae. Gnathopod 2 subchelate; merus/carpus free; dactylus not modified distally. Pereopods 3–7 cuspidactylate. Pereopods 5–7 without setae along posterior margin of the dactylus. Pereopods 6–7 not sexually dimorphic, without row of short setae along posterior margin of dactyli. Pleonites 1–3 without dorsal spines. Pleopods all well developed. Epimera without vertical slits. Uropod 1 rami with apical spear-shaped setae; outer ramus slender, without marginal robust setae. Uropod 3 well developed; ramus longer or subequal in length to peduncle. Telson entire, with 3–9 robust setae per lobe.

Remarks. Pseudorchestoidea brito and P. gracilis are moved to Britorchestia and Sardorchestia respectively. Both species have marginal robust setae on the outer ramus of uropod 1.

Pseudorchestoidea (sensu stricto) is very similar to Platorchestia (group 3) of Miyamoto & Morino (2004). The only significant generic-level differences between these taxa are: the apparently fused articles 3 and 4 of the maxillipedal palp (reduced, button-shaped in Platorchestia (group 3)) and the length of the uropod 3 ramus – subequal or longer than the peduncle in Pseudorchestoidea and shorter in Platorchestia (group 3).

In our diagnosis Pseudorchestoidea only differs from Talorchestia in the length of the ramus to the peduncle of uropod 3 and that is gradational. Morino & Miyamoto (1988) separate Pseudorchestoidea from Talorchestia based on the large eyes, the short, expanded dactylus of pereopod 5; and the modified apical spade-like robust setae of uropods 1 and 2. They also suggest modified pleopods, but this is a very subtle difference and the elongate ramus of uropod 3, but this is not true for the type species P. biolleyi .

As currently defined Pseudorchestoidea is a small genus confined to the tropical eastern Pacific Ocean whose immediate sister taxon appears to be Talorchestia , another small genus confined the the western Pacific Ocean. Distribution. Central America: Costa Rico; El Salvador; Mexico.