Paraflagitopisa excavata sp. nov.

(Figs 1 C, 2–5)

Material examined. Holotype: male (OMNH-Ar-9714), 6.2 mm, off Toyokunizaki coast, Misaki Town, Osaka Prefecture, 34°19'23"N, 135°06'58"E (Fig. 1 C), 4.1 m in depth, gravel and shell bottom beside rock, together with Gammarella cyclodactyla (Hirayama, 1978) and Abludomelita japonica (Nagata, 1965), 6 October 1986, coll. H. Ariyama. Paratypes: 1 male (OMNH-Ar-9715), 4.6 mm, and 1 female (OMNH-Ar-9716), 5.0 mm, same data as holotype.

Description. Male [based on holotype, 6.2 mm (OMNH-Ar-9714) and paratype, 4.6 mm (OMNH-Ar-9715) for right mandible, pereopods 5–7 and pleonal epimera]. Body (Fig. 2) slender, pereonites and pleonites without dorsal setae.

Antenna 1 (Fig. 3 A, A1) with ratio of lengths of peduncular articles 1–3 1:1.0:0.5, article 1 with bundle of lateral setae and distomedial robust seta; accessory flagellum with seta on tip; primary flagellum with 15 articles, last article with distal seta. Antenna 2 (Fig. 3 B) with ratio of lengths of peduncular articles 3–5 1:2.6:2.2; flagellum short, with 7 articles, last article with a few distal setae.

Mandible (Fig. 3 D, D1, E, E1), each incisor bearing 4 cusps, left lacinia mobilis spiniform, right with 4 cusps, accessory blades 5 in left, 7 in right; palp article length ratio 1:2.8: 1.8 in right, article 2 with 4–5 setae ventrally, article 3 with 7 setae. Maxilla 1 (Fig. 3 G, G1), tip of palp article 2 projected in middle, with 2 robust setae. Maxilla 2 (Fig. 3 H), inner plate wider than outer. Maxilliped (Fig. 3 I, I1 – 2), distal end of inner plate bearing 3 short robust setae; outer plate with 8 robust setae; ventral surface of palp article 3 covered with thin setae.

Gnathopod 1 (Fig. 4 A, A1), coxa roundish; basis widened in distal two thirds, posterior margin with long seta in middle; posterior margin of ischium with seta; lateral and medial surfaces of merus covered with thin setae; posterior margin of carpus setose; propodus about 0.9 times as long as carpus, posterodistal corner with 5 small robust setae medially; dactylus short. Gnathopod 2 (Fig. 4 B, B1), coxa roundish trapezoidal; basis widened in distal two thirds, posterior margin with 2 long setae in middle; carpus lobed, posterior margin setose; propodus enlarged, about 3.1 times as long as carpus, posterior margin with several bundle of setae, anteromedial surface sparsely setose; palm largely excavated posteriorly, defined by 2 medial robust setae, middle part of palm with 5 lateral and 3 medial short robust setae; dactylus strong, curved.

Pereopods 3–4 (Fig. 4 C – D), coxae quadrate; posterior margins of bases with several setae; meri slender, widened distally; dactyli narrow, almost straight. Pereopod 5 (Fig. 4 E, E1), posterior lobe of coxa about 0.6 times as long as anterior lobe; basis relatively wide, posterodistal corner swelled; posterior margin and posterodistal corner of merus each with 2 robust setae; anterodistal and posterodistal corners of carpus with 3 and 4 setae, respectively; anterior margin and anterodistal and posterodistal corners of propodus bearing 2, 1 and 1 robust setae, respectively; dactylus narrow. Pereopod 6 (Fig. 4 F, F1) about 1.4 times as long as pereopod 5; posterior lobe of coxa about 0.7 times as long as anterior lobe; basis relatively wide, posterodistal corner swelled; posterior margin and posterodistal corner of merus each with 2 robust setae; anterodistal and posterodistal corners of carpus with 5 and 3 setae, respectively; anterior margin and anterodistal and posterodistal corners of propodus bearing 3, 1 and 1 robust setae, respectively; dactylus narrow. Pereopod 7 (Fig. 4 G, G1) about 1.3 times as long as pereopod 6; coxa trapezoidal; basis relatively wide, posterodistal corner swelled; posterior margin and posterodistal corner of merus each with 3 setae; anterior and posterior margins of carpus setose, anterodistal and posterodistal corners with 2 and 7 setae, respectively; anterior and posterior margins of propodus setose; dactylus narrow.

Pleonal epimera (Fig. 5 A), epimeron 2 with thick seta ventrally, posteroventral corner with minute seta; epimeron 3 with 1 thick and 1 thin setae ventrally, posteroventral corner minutely projected, bearing minute seta. Pleopods 1–3 (Fig. 5 B – D), pleopod 3 shortest; peduncles each with distal projection; inner and outer rami with 10 and 11 articles in pleopod 1, 9 and 10 articles in pleopod 2, and 8 and 9 articles in pleopod 3, respectively. Uropod 1 (Fig. 5 E) long; peduncle long, bearing 2 ventrofacial, 4 dorsomedial, 6 dorsolateral and 1 medial robust setae, distomedial and distolateral corners with 2 and 1 long robust setae, respectively; inner ramus 63 % length of peduncle, with 1 medial, 1 lateral and 3 distal robust setae; outer ramus 56 % length of peduncle, with 2 medial and 4 distal robust setae. Uropod 2 (Fig. 5 F) short, about 0.7 times as long as uropod 1; peduncle short, bearing 3 dorsomedial robust setae, distomedial and distolateral corners with 2 and 1 robust setae, respectively; inner ramus about same length as peduncle, with 3 medial and 5 distal robust setae; outer ramus 83 % length of peduncle, with 1 medial, 3 lateral and 3 distal robust setae. Uropod 3 (Fig. 5 G) very large, about 1.9 times as long as uropod 1; peduncle short, with 2 ventral robust setae, distolateral corner bearing 4 setae; inner ramus about 1.8 times as long as peduncle, with 3 medial, 3 lateral and 4 distal robust setae; outer ramus about 5.3 times as long as peduncle, article 1 with several medial and 2 lateral setae, distomedial and distolateral corners with 6 and 2 robust setae, respectively, article 2 almost same length as article 1, with several setae on medial and lateral margins, distal margin setose. Telson (Fig. 5 H), breadth subequal to length; lateral margins with 1–2 robust setae, distal margins bearing 2–3 robust setae, dorsal surface with 2 pairs of plumose setae.

Female [paratype, 5.0 mm (OMNH-Ar-9716)]. Generally similar to male except for gnathopods and oostegites. Gnathopod 1 (Fig. 5 I, I1), coxa rhomboidal; basis narrower, carpus and propodus wider than that of male; propodus 96 % as long as carpus, posterodistal corner with 4 small robust setae medially. Gnathopod 2 (Fig. 5 J, J1) smaller than that of male; coxa narrower; propodus shorter, about 1.6 times as long as carpus, palm smoothly curved, defined by 2 medial robust setae, posterior margin with several bundle of setae, anteromedial surface setose; dactylus slender.

Etymology. From the Latin excavata (= excavate), referring to the shape of male gnathopod 2.

Habitat. Marine, subtidal. Among gravel and shell.