Mauritiorchestia, Green & Appadoo & Lowry & Myers, 2021

Green, M. A. A., Appadoo, C., Lowry, J. K. & Myers, A. A., 2021, A new genus and species of sand-hopper, Mauritiorchestia fayetta gen. nov., sp. nov (Amphipoda, Talitridae) from Mauritius, Zootaxa 5068 (2), pp. 295-300 : 296-297

Mauritiorchestia gen. nov.

Type species. Mauritiorchestia fayetta sp. nov.

Included species. Mauritiorchestia is currently monotypic.

Category. Mascupod.

Ecological type. Sand-hopper.

Etymology. A compound noun derived from the name of the country and the name of a related genus.

Diagnostic description (male).

Head. Antenna 1 short, not reaching midpoint of peduncular article 5 of antenna 2. Antenna 2 peduncular articles incrassate. Mandible left lacinia mobilis 5-cuspidate. Maxilla 1 palp absent. Labium without inner lobes. Maxilliped palp article 2 with distomedial lobe; article 4 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 4 groups of robust setae, ‘subtriangular’ with well-developed posterodistal lobe, palm transverse; dactylus simplidactylate. Gnathopod 2 sexually dimorphic; subchelate; propodus palm acute, rounded distally and sinuous, with small to large midpalmar sinus, without proximal sinus, without large distal sinus, without proximal spine or thumb defining palm; without large projection near dactylar hinge; dactylus not modified distally, blunt, fitting into sulcus internally. Pereopods 3–5 cuspidactylate, 6–7 simplidactylate. Pereopod 4 significantly shorter than pereopod 3; carpus significantly shorter than that of pereopod 3; dactylus amplidactylate, thickened proximally with notch midway along posterior margin. Pereopod 6 subequal in length to pereopod 7; not sexually dimorphic; basis moderately expanded; male merus expanded, carpus not expanded. Pereopod 7 not sexually dimorphic; basis broadly expanded, posterior margin smooth or minutely serrate margin without setae, posterodistal lobe present, rounded, produced downwards almost to merus; merus expanded distally, subtriangular, anterior margin slightly straight; carpus expanded, subrectangular, slightly shorter than propodus; propodus slender.

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 1 row. Uropod 2 exopod without marginal robust setae; endopod with marginal robust setae in 1 row. Uropod 3 ramus subequal in length to peduncle. Telson completely cleft, with 6 robust setae per lobe.

Remarks. Mauritiorchestia is a distinctive Indian Ocean genus. Based on an incrassate second antenna, gnathopod 1 with palmate lobes on the carpus and propodus and uropod 1 exopod without marginal robust setae, it is most similar to the north-western Pacific genus Sinorchestia Miyamoto & Morino, 1999 and the wide-ranging genus Platorchestia Bousfield, 1982 . Sinorchestia differs significantly from Mauritiorchestia in having a ventral plate on the third peduncular article of antenna 2, a parachelate first gnathopod and a large posteroproximal sinus on the dactylus of gnathopod 2. Platorchestia differs from Mauritiorchestia mainly in having a cuspidactylate first gnathopod and the exopod of uropod 2 with marginal robust setae in one row.

Distribution. Mauritius, Western Indian Ocean.