Africorchestia, Lowry, James K. & Coleman, Charles Oliver, 2011

Lowry, James K. & Coleman, Charles Oliver, 2011, Africorchestia a new genus of sand-hoppers (Crustacea: Amphipoda: Talitridae) from western Africa and south-western Europe, Zootaxa 2825, pp. 55-68 : 56-58

Africorchestia gen. nov.

Description. Antenna 2 peduncular articles narrow; with many large robust setae. Mandible left lacinia mobilis 5- dentate. Maxilliped palp article 2 distomedial lobe well developed, article 4 reduced, button-shaped. Gnathopod 1 parachelate; posterior margin of carpus and propodus each with lobe covered in palmate setae in male, posterior margin of merus, carpus and propodus each without lobe covered in palmate setae in female; palm transverse in male. Gnathopod 2 subchelate in male; mitten-shaped in female. Pereopods 2–4 coxae as wide as deep. Pereopods 3–7 cuspidate. Pereopods 6–7 longer than pereopods 3–5, with slender setae along posterior margin of dactyli. Pereopod 6 basis expanded in male. Pleonites 1–3 with dorsal sculpturing (spines or ridges) in males (absent in females where known). Pleopods all well developed. Pleopod 1 peduncle with marginal robust setae. Uropod 1 peduncle distolateral robust seta present; inner and outer rami with marginal robust setae. Uropod 2 not sexually dimorphic; inner and outer rami with marginal robust setae. Uropod 3 ramus longer than peduncle or subequal in length to peduncle. Telson with marginal and apical robust setae, with 3 to 6 robust setae per lobe.

Type species. Orchestia spinifera Mateus, 1962 , original designation.

Included species. Africorchestia includes 5 species: A. fischeri (H. Milne Edwards, 1830) ; A. quadrispinosa ( K.H. Barnard, 1916) ; A. skoogi ( Stebbing, 1922) ; A. spinifera ( Mateus, 1962) ; A. tricornuta ( Shoemaker, 1920) . Remarks. Africorchestia appears to be most similar to Americorchestia Bousfield, 1991 and Sardorchestia Ruffo in Tafani et al., 2004. Americorchestia and Africorchestia are similar in most characters including the male parachelate first gnathopods and the characteristic third uropods with the ramus longer than the peduncle. They differ in the pleosome which is sculptured in Africorchestia , in pereopod 6 which is sexually dimorphic in Africorchestia , and in the dactyli of pereopods 6 and 7 which have slender setae along the posterior margin in Africorchestia .

Africorchestia is also very similar to Sardorchestia . They differ significantly in the dactyli of pereopods 6 and 7 with setae along the posterior margin in Africorchestia (absent in Sardorchestia ); in pereopod 6 which is sexually dimorphic in Africorchestia ; and pleonites 1–3 rugose or with spines (absent in Sardorchestia ).

Americorchestia and Sardorchestia are very similar. In Sardorchestia the male gnathopod 2 propodus has a large posteroproximal thumb and there are more robust setae on the telson , but this character appears to be continuous between these genera. Based on the morphology Americorchestia and Sardorchestia could be synonymised and the Mediterranean species Sardorchestia pelecaniformes ( Bellan-Santini & Ruffo, 1986) and Talorchestia ugolini Bellan-Santini & Ruffo, 1991 would both fall into Americorchestia .