Microjassa Stebbing 1899

Microjassa Stebbing, 1899b [Japanese name: Hosohige-kamakiri-yokokoebi-zoku] Microjassa Stebbing, 1899b: 240.— Stebbing, 1906: 651.— Chevreux & Fage, 1925: 350.—J.L. Barnard, 1969b: 279.—J.L. Barnard, 1973: 26.— Lincoln, 1979: 564.— Myers, 1989a: 438.—J.L. Barnard & Karaman, 1991: 213.— Conlan, 1995: 334.— Myers & Lowry, 2003: 472.— Conlan, 2021: 61 (key). Type species. Podocerus cumbrensis Stebbing & Robertoson, 1891, monotypy. Diagnosis. Body laterally compressed, pereonites and urosomites smooth. Rostrum and ocular lobes short, antennal sinus deep. Eyes ordinary. Antenna 1 ca. 0.5–1.0 times as long as antenna 2; peduncular article 3 longer than article 1; accessory flagellum 1-articulate; primary flagellum short, with 2–4 articles. Antenna 2 flagellum also short, with 2–4 articles. Mandibular palp article 3 narrower than long; maxilla 1 inner plate bare. Coxae long, strongly overlapping; coxae 1, 5 half or shallower than coxae 2–4; coxa 4 excavate posterodorsally; medial surface of coxa 2 or 3 with minute ridges for stridulation in adult male. Gnathopod 1 in both sexes small, subchelate; propodus ca. 1.8–3.7 times length of carpus, palm smooth. Male gnathopod 2 much larger than gnathopod 1 (propodus length ratio: ca. 1.7–3.3), subchelate; basis with stridulating nodules or ridges in adult; carpus very short; propodus dilated, often with large chela or thumb posteroproximally; dactylus ca. 0.5–1.0 times length of propodus. Female gnathopod 2 smaller than that in male, slightly larger than gnathopod 1, subchelate; propodus longer than carpus, palm smooth. Pereopods 3, 4 normal, similar; bases slightly inflated, propodi not prehensile, dactyli shorter than propodi. Pereopods 5–7 similar to each other, progressively longer or almost same length; bases expanded, ischia without posterior wing. Pleopods normal. Uropods biramous, peduncles without lateral row of setae; uropod 1 peduncle with or without inter-ramal process, rami slightly unequal, longer than or as long as peduncle; uropod 3 peduncle long, with 0–5 mid-dorsal and 1–2 distal robust setae, but without a cluster of distolateral setae; both rami very short, outer ramus recurved apically, with 3–16 apicolateral minute cusps, inner ramus slightly longer than or subequal to outer ramus, narrow, tapering, usually with a minute robust seta on tip. Telson entire, various-shaped. Included species (11 species). Microjassa bahamensis Conlan, 1995; M. barnardi Conlan, 1995; M. boreopacifica Conlan, 1995; M.bousfieldi Conlan, 1995; M.cumbrensis; M.excavata sp. nov.; M.floridensis Conlan, 1995; M. litotes J.L. Barnard, 1954; M. macrocoxa Shoemaker, 1942; M. tetradonta Conlan, 1995; and M. vestigialis sp. nov. Remarks. The distinctive characters of Microjassa are (1) coxae 2–4 deeper than coxae 1 and 5, (2) coxa 4 excavate posterodorsally, and (3) medial surface of coxa 2 or 3 with minute ridges and gnathopod 2 basis with nodules or ridges in adult male. Especially the character (3) is unique in the tribe Ischirocerini. Distribution. Pacific North America, Atlantic North America, Atlantic Europe, Mediterranean Sea (Conlan 2021), and East Asia (present study). Depth range: 0–161 m (Conlan 2021, present study).