Morinoia Lowry & Myers, 2019

Lowry, J. K. & Myers, A. A., 2022, Platorchestiinae subfam. nov. (Amphipoda, Senticaudata, Talitridae) with the description of three new genera and four new species, Zootaxa 5100 (1), pp. 1-53 : 31-33

Morinoia Lowry & Myers, 2019

Platorchestia Bousfield, 1982: 26 (in part.)

Platorchestia group 3 of Miyamoto & Morino, 2004: 69 (in part).

Morinoia Lowry & Myers, 2019: 61 , fig. 27.

Type species. Platorchestia paludosus Cheng, Nakazono, Lin & Chan, 2011 , original designation.

Included species. Morinoia contains 3 species: M. humicola ( Martens, 1868) ; M. japonica ( Tattersall, 1922) ; M. paludosus ( Cheng, Nakazono, Lin & Chan, 2011) .

Ecological type. Field-hopper, riparian-hopper and marsh-hopper.

Habitat. Marshes, under fallen leaves and grass in coastal areas.

Diagnostic description (male). Based on Cheng et al. (2011), Miyamoto & Morino (2004), Morino & Dai (1990).

Head. Antenna 2 peduncular articles slender or slightly incrassate. Mandible left lacinia mobilis 5-cuspidate. Labium without inner lobes, or with possible vestigial inner lobes. Maxilliped palp article 2 with distomedial lobe; article 4 small, distinct, or reduced, button-shaped, or fused with article 3.

Pereon. Gnathopod 1 sexually dimorphic; subchelate; posterior margin of carpus and propodus each with lobe covered in palmate setae; propodus anterior margin with 2 groups of robust setae or with 3 groups of robust setae, ‘subtriangular’ with well-developed posterodistal lobe, palm transverse or obtuse; dactylus simplidactylate. Gnathopod 2 subchelate; propodus palm acute, evenly rounded, without palmar sinuses; without proximal spine or thumb defining palm; dactylus short, recurved distally. Pereopods 3–7 dactyli bicuspidactylate. Pereopod 4 subequal or slightly shorter than pereopod 3; carpus similar in length to that of pereopod 3; dactylus amplidactylate or homobasidactylate, similar to pereopod 3 dactylus, not thickened proximally or notched or short with mini-wavy posterior margin. Pereopod 6 subequal in length to pereopod 7, not incrassate; basis moderately expanded; male merus expanded, carpus not expanded. Pereopod 7 not incrassate; basis broadly expanded, posterior margin with distinct minute serrations, each with a small seta or smooth with sparse seta, posterodistal lobe present, shallow, broadly rounded; merus expanded distally, subtriangular, anterior margin slightly convex; carpus unexpanded, subrectangular; carpus shorter than propodus; propodus broad, or propodus slender; length 5.7–7.9 × width; propodus without large distal tuft of setae. Oostegites (female) setae with simple smooth tips.

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 or with marginal robust setae in 2 rows ( M. japonica ). Uropod 2 exopod with marginal robust setae in 1 row; endopod with marginal robust setae in 2 rows ( M. japonica ). Uropod 3 ramus subequal in length to peduncle, or shorter than peduncle. Telson completely cleft or apically incised, with 3–6 robust setae per lobe.

Remarks. Morinoia appears to be most similar to Miyamotoia and Yamatorchestia , both terrestrial genera from Japan and Taiwan. Aside from the well-developed pleopods in Morinoia (all reduced in Miyamotoia and Yamatorchestia ), Morinoia has an expanded pereopod 6 merus (not expanded in Miyamotoia and Yamatorchestia ), the pereopod 7 merus is expanded and subtriangular in shape (unexpanded in Miyamotoia and Yamatorchestia ) and the distolateral robust seta of uropod 1 is absent in Morinoia (present or absent in Miyamotoia and present in Yamatorchestia ).

Distribution. Korea, China, Japan, Taiwan ( Martens 1868, Tattersall 1922, Morino 1999, Miyamoto & Morino 2004 and Cheng et al. 2011).