Mecodelphys edentatus gen. et sp. nov.

(Figs. 383, 384)

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21419), paratypes (6 intact ♀♀, MNHN-IU-2014-21420), and dissected paratypes (2 ♀♀, figured) from the colonial ascidian Lissoclinum taratara Monniot C. & Monniot F., 1987 (MNHN-IT-2008-4990 = MNHNA2/LIS/162), CRRFCRCHO 297, Cape Rodney Pass, Papua New Guinea (10°15.66 Ś, 148°22.27 É), depth 31 m, 11 June 1998 .

Etymology. The name is from the Latin e (=without) and dentat (=toothed), alluding to the absence of a coxal gnathobase in the new species.

Descriptionoffemale. Body(Fig.383A) Doropygus - like in form, surface ornamented with numerous, minute setules. Prosome divisible by weak constrictions into cephalosome, first and second pedigerous somites, and fused third and fourth pedigerous somites; dorsal cephalic shield expanded ventrolaterally, bearing pair of small, acutely pointed, spiniform processes posterolaterally (Fig. 383C). Fused third and fourth pedigerous somites swollen, forming brood pouch. Free urosome (Fig. 383B) 5- segmented: genital somite short, only partially articulated from brood pouch; 4 abdominal somites setulose, 85×144, 69×131, 38×118, and 80×107 μm, respectively. Caudal ramus (Fig. 383D) tapering, covered with setules, about 2.7 timeslongerthan wide (75×28 μm), slightly shorter than anal somite, tipped with short, spiniform process: armedwith 5 smallsetae (2 outer lateral, 1 outer subdistal, and 2 small distal).

Rostrum (Fig. 383E) rather large, 100×89 μm, evenly tapering towards pointed apex, surface covered with setules. Antennule (Fig. 383F) stout, 148 μm long, covered with setules, unsegmented but with 2 partial articulations on posterior surface; armed with about 17 small setae. Antenna (Fig. 383G) slender and 3- segmented; coxashortand unarmed; secondsegment (fused basis and first endopodal segment) also unarmed, with vestige of articulation near middle; third segment (second endopodal segment) about 4.2 timeslongerthan wide (101×24 μm); armed with 4 tiny setae (1 proximal, 2 subdistal, and 1 distal) plus small terminal claw, about 0.2 times as long as segment.

Labrum (Fig. 383H) large with rounded posterior margin. Mandible consisting only of palp, without coxal gnathobase; palp unsegmented with lobate rami; inner lobe broad and blunt; each lobe armed with 4 naked setae. Maxillule (Fig. 384A), maxilla (Fig. 384B), and maxilliped(Fig. 384C)eachrepresentedby lobe.Maxillule narrowing distally, with subdistal constriction, armed with 4 equal setae on apex. Maxilla tipped with 1 short seta, and maxilliped with 1 longer seta. All mouthparts ornamented with scattered setules.

Legs 1–4 (Fig. 384 D-G) biramous, with unsegmented protopods armedwith smallouter seta; both rami elongate, digitiform, fused with or incompletely articulated with protopod, covered with setules. Leg 1 distinctly smaller than posterior swimming legs. Endopods slightly longer than exopods in legs 1–3, but less than one-third as long as exopod in leg 4. Lengths of rami: 153, 258, 251, and 207 μm, respectively, for exopods of legs 1–4; and 167, 275, 285, and 64 μm, respectively, for endopods of leg 1-4. Endopods unarmed, but exopods of legs 1–4 armed with few, small setae distally, 2 or 3, 1, 2, and 3, respectively.

Leg 5 (Fig. 384H) represented by 2 ventral processes on each side of somite; outer protopodal process tipped with 1 seta; inner exopodal process conical, pointed apically, bearing 1 seta on its outer margin.

Male. Unknown.

Remarks. The caudal ramus of M. edentatus gen. et sp. nov. bears 5 smallsetae and a claw-like distal process. It can be inferred that the latter process is derived from the fusion of a seta to the ramus.