Africorchestia Lowry & Coleman, 2011

Lowry, J. K. & Baldanzi, S., 2016, New talitrids from South Africa (Amphipoda, Senticaudata, Talitroidea, Talitridae) with notes on their ecology, Zootaxa 4144 (2), pp. 151-174 : 152

Africorchestia Lowry & Coleman, 2011

Africorchestia Lowry & Coleman, 2011: 56 .

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

Included species. Africorchestia includes 5 species: A. fischeri (H. Milne Edwards, 1830) ; A. meridionalis sp. nov.; A. quadrispinosa ( K.H. Barnard, 1916) ; A. skoogi (Stebbing, 1922) ; A. spinifera (Mateus, 1962) ; A. tricornuta ( Shoemaker, 1920) .

Ecological type. Sand-hoppers (supralittoral, substrate-modifying talitrids of sandy beaches).

Diagnostic description. Head. Eye large (greater than 1/3 head length). Antenna 1 short, not longer than peduncular article 4 of antenna 2. Antenna 2 peduncular articles slender; peduncular article 3 without plate or process ventrally. Labrum epistome without robust setae. Mandible left lacinia mobilis 5-cuspidate. Maxilliped palp article 2 with distomedial lobe; article 4 fused with article 3.

Pereon. Gnathopod 1 sexually dimorphic; parachelate; posterior margin of carpus and propodus each with lobe covered in palmate setae; dactylus longer than palm, palm transverse. Gnathopod 2 subchelate; posterior margin of merus, carpus and propodus each without lobe covered in palmate setae; dactylus not modified distally, blunt; carpus longer than propodus; palm extremely acute; dactylus longer than propodus. Pereopods 3–7 bicuspidactylate. Pereopod 4 dactylus thickened proximally with notch midway along posterior margin. Pereopod 5 dactylus long, slender, not inflated or short, inflated. Pereopods 6–7 with row of short setae along the posterior margin of the dactyli. Pereopod 6 sexually dimorphic (basis broadly expanded), longer than pereopod 7. Pereopod 7 not sexually dimorphic (no articles expanded); propodus setation without large distal tuft of setae. Female: oostegites setae with simple smooth tips.

Pleon. Pleonites 1–3 with dorsal spines. Pleopods all well developed. Epimera 1–3 slits absent. Uropod 1 peduncle distolateral robust seta absent, rami with or without apical spear-shaped setae; inner ramus with marginal robust setae in 2 rows; outer ramus with marginal robust setae in one row. Uropod 2 rami with or without apical spear-shaped setae. Inner ramus with marginal robust setae in 2 rows; outer ramus with marginal robust setae in 1 row. Uropod 3 ramus subequal in length to or longer than peduncle. Telson broader than long, tapering distally or rounded distally. Telson apically incised or entire.

Remarks. In the original diagnosis of Africorchestia the maxillipedal palp article 4 was considered to be reduced and button-shaped, but new scanning electron micrographs show that it is fused to maxillipedal palp article 3.

Africorchestia is the only known talitrid genus with dorsal spines on pleonites 1–3. It shares with Pseudorchestoidea Bousfield, 1982 a row of short setae on the posterior margin of the dactyli of pereopods 6–7. At least one species of Africorchestia , A. tricornuta ( Shoemaker, 1920) has apical spear-shaped setae on the rami of uropods 1–2, an apparent powerful synapomorphy that it shares with Americorchestia Bousfield, 1991 , Pseudorchestoidea , and Sardorchestia Ruffo, 2004 . Another species, Africorchestia skoogi (Stebbing, 1922) has an inflated dactylus on pereopod 5, an apparent powerful synapomorphy that it shares with Britorchestia Lowry & Bopiah, 2012 , Pseudorchestoidea and Sardorchestia .