Metodius, Ariyama, 2021

Ariyama, Hiroyuki, 2021, Five species of the family Odiidae (Crustacea: Amphipoda) collected from Japan with descriptions of a new genus and four new species, Zootaxa 5067 (4), pp. 485-516 : 487

Metodius gen. nov.

[Japanese name: Kawari-subeyokoebi-zoku, new]

Type species. Metodius cyanomaculatus sp. nov.

Diagnosis. Body, anterodorsal corner of pereonite 1 slightly produced; dorsal projections of pereonites 1–5 absent, those of pereonite 6, 7 and pleonites absent or present; posterolateral margin of pleonite 3 with acute, upwardly directed projection at midpoint. Eyes longish reniform. Antenna 1, peduncular article 2 shorter than article 1; accessory flagellum 1-articulated; primary flagellum with many aesthetascs in male. Upper lip, tip incised asymmetrically. Mandible slender; incisor wide, fan-shaped; lacinia mobilis present on left side, also fan-shaped; accessory blades developed; molar pear-shaped; palp long, slightly distal to molar. Lower lip, outer lobes not notched inside, tips projected. Maxilla 1 short; inner plate small, bearing 1–3 apical setae; outer plate acutely projected apically, with many robust setae on mediodistal margin; palp 1-articulated, short, tip rounded, without setae. Maxilla 2, inner plate shorter than outer plate, mediodistal margins of both plates strongly setose. Maxilliped, inner plate setose; outer plate short, not reaching distal end of palp article 2; palp 4-articulated, article 2 medial margin slightly expanded, article 4 long triangular. Coxa 1 relatively small, coxae 2–4 progressively wider and longer; inner surfaces of coxae 2–4 each with “holder structure” (its triangular process holding anterior coxa together with coxal plate). Gills present on gnathopod 2–pereopod 6. Oostegites of female present on gnathopod 2–pereopod 5. Gnathopod 1, propodus projected posterodistally, projection with short robust seta; dactylus small. Gnathopod 2, propodus large, ca. 0.9–1.0 times of coxal length, palm weakly oblique, defined by small projection, margin minutely serrated. Pereopods 3, 4 slender, 5–7 stout; meri projected distally, projections not reaching distal end of carpi, dactyli each with nail. Uropods, inner ramus of uropod 3 relatively wide; peduncles of uropods 1, 2 and both rami bearing many robust setae. Telson minutely cleft or entire, lateral margins each with pair of penicillate setae.

Etymology. From the Greek met (= beyond) and Odius (type genus of the family).

Species included. Metodius cyanomaculatus sp. nov. and M. leucomaculatus sp. nov.

Remarks. Metodius gen. nov. differs from the other odiid genera in the short maxilla 1 palp with rounded bare tip and the large gnathopod 2 propodus almost the same length as the coxa 2.

Distribution. Japan only.