Mauritiorchestia fayetta sp. nov.

(Figs 1, 2)

Platorchestia fayetta Beeltah & Appadoo, 2017: 44 (nomen nudum).

Material Examined. HOLOTYPE, 1 male, 9.8 mm from Poste la Fayette (20°8.2’S, 57°44.5’E), Mauritius, on coastal sandy substrate with huge amount of beach wrack algae, A. Green, (20 November 2014), NHM/ 2021/01/01 . PARATYPES: 1 female, 8.6 mm, NHM/ 2021/02/01, other paratypes; 3 males NHM/ 2021/03/01, 5 females NNHM / 2021/04/01, same data as holotype; 6 females, 4 males, same data as holotype, author’s (CA) collection, Mauritius .

Etymology. Named after the type locality Poste la Fayette.

Description. Male holotype, length. 9.8 mm.

Body laterally compressed. Head height equal to length. Eyes medium sized round. Antenna 1 shorter than peduncle of antenna 2; peduncular article 2 longer than peduncular article 1; not geniculate; flagellum with 5 articles and a small terminal article. Antenna 2 incrassate, longer than antenna 1; not geniculate; peduncular articles broad and long with sparse, small and robust setae; peduncular article 2 longer than peduncular article 1; flagellum longer than peduncle, 13 articles and a small terminal article. Mandible palp absent; left lacinia mobilis 5 cuspidate; incisor 5 dentate; setal row with 4 plumose setae. Maxilla 1 palp absent; inner plate with setae on margin and two strong apical plumose setae; outer plate with 7 strong medially serrate robust setae. Maxilla 2 inner plate with round distal margin with one strong, long plumose seta on lateral margin; outer plate with round distal margin with especially long setae on apex and fine setae on lateral margin. Maxilliped palp with 3 well developed articles, article 4 vestigial, visible only from ventral view. Lower lip with narrow lobes and wide shoulders; apical setal tuft present.

Gnathopod 1 sexually dimorphic; subchelate; palmate lobe present on posterior margin of carpus and propodus; propodus subtriangular; palm transverse; dactylus as long as palm, triangular, thick. Gnathopod 2 sexually dimorphic; subchelate; larger and more robust than gnathopod 1; coxa as long as wide; basis broad; carpus triangular; propodus massive, with anterior margin convex, palm sinuous, notch in the middle of palm, row of marginal setae on palm; dactylus as long as palm, inner face with minute robust setae on margin; dactylus fitting into sulcus internally. Coxae 2–4 as long as broad. Pereopod 3 longer than pereopod 4; cuspidactylate. Pereopod 4 cuspidactylate with a thick dactylus compared to pereopod 3. Pereopod 5 shorter than pereopod 6; coxa bilobate with small robust setae on each lobe; propodus longer than carpus; cuspidactylate. Pereopod 6 not sexually dimorphic, coxa weakly serrate; merus, carpus and propodus all broadened, propodus longer than carpus, homosimplidctylate. Pereopod 7 posterior distal margin of basis serrate; merus and carpus subrectangular; homosimplidactylate.

Uropod 1 biramous; 16 robust setae in two rows on peduncle; exopod 0.7 x as long as peduncle; endopod with 5 setae on inner margin; exopod without marginal robust setae. Uropod 2 biramous; inner margin of peduncle with 3 robust setae; exopod 0.8 x as long as peduncle; rami subequal in length, inner margin of endopod with 3 robust setae; exopod without marginal robust setae Uropod 3 uniramous; ramus 0.9 x as long as peduncle; peduncle with 4 robust setae; ramus narrowing distally, with 4 setae on inner margin and 4 apical setae. Telson entire; broader than long; apically incised; 6 robust setae per lobe; dorsal midline entire.

Female (sexually dimorphic characters). 8.6 mm. Gnathopod 1 parachelate; propodus subrectangular; lobe absent at posterior margin of carpus and propodus; dactylus longer than palm. Gnathopod 2 mitten-shaped, smaller than gnathopod 2 in males; coxa with protuberance; basis enlarged and elliptical; dactylus shorter than of males and shorter than palm; palm with 3 small robust setae. Pereopod 6 coxa subquadrate with protuberance; basis posterior margin convoluted; basis narrower than in male; merus, carpus and propodus unexpanded. Pereopod 7 merus and carpus unexpanded.

Distribution. Poste la Fayette, Mauritius.