Meximaera Barnard, 1969a

Ariyama, Hiroyuki, 2020, Species of the Maera - clade collected from Japan. Part 3: genera Maera Leach, 1814, Meximaera Barnard, 1969 and Orientomaera Ariyama, 2018 (addendum), with a key to Japanese species of the clade (Crustacea: Amphipoda: Maeridae), Zootaxa 4743 (4), pp. 451-479 : 463-464

Meximaera Barnard, 1969a

[Japanese name: Mekishiko-sunnariyokoebi-zoku, new]

Meximaera Barnard, 1969a: 209 .— Krapp-Schickel, 2008a: 22.— Krapp-Schickel, 2008b: 1425.— Lowry & Myers, 2013: 36.

Type species. Meximaera diffidentia Barnard, 1969a , monotypy.

Emended diagnosis. Body smooth. Head, rostrum obsolescent, lateral cephalic lobe rounded, antennal sinus shallow, anteroventral corner rounded or projected; eyes oval, about 0.15–0.3 times as long as head. Antennae slender; antenna 1, peduncular articles 1–2 longer than article 3, accessory flagellum with 4–6 articles. Mandible, palp article length 2>3>1, article 1 usually without distal tooth. Coxae short, anteroventral corner of coxa 1 rounded or produced acutely, coxae 5–6 lobate; gills present on coxae 2–6, oostegites present on coxae 2–5. Gnathopod 1 subchelate; carpus longer than or subequal to propodus; propodus longish ovate, palm oblique. Gnathopod 2 larger than gnathopod 1, symmetrical, subchelate; merus with or without acute posterodistal spine; carpus short, lobate; propodus longish ovoid, length 1.6–2.1 times width; palm moderately or strongly oblique, margin with several robust setae; dactylus with single seta on anterior margin. Pereopods, dactyli simple; pereopods 3–4 slender; pereopods 5 – 7, bases more or less expanded. Uropods biramous; uropods 1–2, peduncle and both rami with many robust setae; uropod 3, peduncle short, rami subequal in length, wide, outer ramus 1.5 – 3.3 times as long as peduncle, distal margins of rami truncate, with several robust setae, longest distal seta of outer ramus 0.1 – 0.8 times as long as outer ramus. Telson slightly longer than or as long as wide, deeply incised, each lobe with 2 – 5 distal robust setae, longest robust seta 0.3 – 0.9 times of telson.

Included species (4). Meximaera briani Krapp-Schickel, 2008b ; M. diffidentia Barnard, 1969a ; M. mooreana ( Myers, 1989) ; M. tulearensis ( Ledoyer, 1972) .

Remarks. This genus resembles Ruffomaera Krapp-Schickel, 2008b and a part of Orientomaera Ariyama, 2018 in having the symmetrical male gnathopod 2 with oblique palm, the simple dactyli of the pereopods 3 – 7, and the truncate tips of the uropod 3 rami. However, Meximaera differs from Ruffomaera in the smooth posterior margins of the pleonal epimera 2 – 3 and the smooth posterodorsal margins of the urosomites 1 – 2 ( Krapp-Schickel 2008b), and from Orientomaera in the fewer (<15) and larger robust setae on the gnathopod 2 palm ( Ariyama 2018).