Goniodelphys nosybensis Kim & Boxshall 2020, sp. nov.

Goniodelphys nosybensis sp. nov.

(Figs. 109, 110)

Type material. Holotype ♀ (dissected and mounted on a slide, MNHN-IU-2014-21251) from Polycarpa pigmentata (Herdman, 1906) (MNHN-IT-2008-6638 = MNHNS1/POL.B/350), MUA 68, Nosy Be, Madagascar, Laboute coll., 1995.

Etymology. This species is named after the type locality, Nosy Be, Madagascar.

Descriptionoffemale.Body(Fig.109A)compressed, 3.70 mm long. Prosome 2.85 mm long, clearly segmented. Fourth pedigeroussomite forming brood pouch, tapering in posterior half (in lateral view), longer than anterior part of prosome. Fifth pedigerous somite completely fused with fourth. Free urosome (Fig. 109B) slender, 5-segmented; genitalsomite 285×406 μm, slightly narrowing posteriorly, with copulatory pore on ventral surface. Four abdominal somites 460×370, 400×327, 285×267, and 152×194 μm, respectively; firsttothird somites longer than wide; setulose on all surfaces. Anal somite (Fig. 109C) roundly protruded posteroventrally, highly sclerotized. Caudalramus (Fig. 109C) about 1.6 times longer than wide (116×73 μm), narrowing distally, armed with 2 claws and 4 setae; lengths of claws very unequal, 110 and 45 μm; setae naked, ventrodistal seta distinctly longerthan other 3.

Rostrum (Fig. 109D) triangular, 175×170 μm, with blunt apex. Antennule (Fig. 109E) attenuated distally, 375 μm long, 8-segmented; first and second segments with 6 and 10 setae, respectively; setation of other segments uncertain due to numerous missing setae; several setae pinnate.Antenna (Fig. 109F) 4-segmented, including short coxa; basis with exopod respresentedby 1 largeand 1 small seta at outer distal corner, ornamented with small patch of setules on inner margin; first endopodal segment slightly longer than wide, with 1 seta on inner margin; compound distal endopodal segment about 2.5 times longer than wide (118×48 μm), armedwith 10 setae (distal 3 blunt tipped) plus terminal claw more than half as long as segment.

Labrum (Fig. 109G) with semicircular, setulose posteromedianlobe. Mandible (Fig. 109H) with 5 teeth, 2 proximal setae, and 3 needle-like spinules between distal second and third teeth; basis with 1 seta on medial margin; exopod 2-segmented with 3 and 2 equal setaeon first and second segments, respectively; endopod 2-segmented and armed with 5 setae (distalmost seta longest and naked) on first segment and 9 setae on second. Maxillule (Fig. 109I) with 9 setae on arthrite, 1 on coxal endite, 2 on epipodite, 3 one medial margin of basis, 3 on exopod and 4 on endopod. Maxilla (Fig. 110A) 5-segmented; syncoxa with 9 setae (3, 1, 2, and 3 on first to fourth endites, respectively), basis with 3 setae, distalseta stiff, claw-like; endopod with 1, 1, and 4 setae on first to third segments, respectively, (1 seta on third endopodal segment small, liable to be overlooked). Maxilliped (Fig. 110B) lobate, armed with 10 setae (8 medial and 2 apical).

Legs 1–4 with 3-segmented rami but articulation between second and third endopodal segments of leg 1 incomplete (Fig. 110C). Exopods distinctly longerthan endopods in legs 2 (Fig. 110D), 3 and 4 (Fig. 110E). Inner coxal seta absent in legs 1–4. Outer seta on basis large and pinnate in leg 1, but small and naked in legs 2–4. Inner distal spine on basis of leg 1 straight, smooth, extending to middle of second endopodal segment. Armature formula for legs 1–4 as follows:

Leg 5 (Fig. 110F) consistingof free protopod and exopod; protopod withnaked setaon outer margin; exopodal segment subrectangular, about 1.9 times longer than wide (55×29 μm), armed with 2 naked setae, distal seta 68 μm long and subdistal seta 21 μm and blunt at tip. Leg 6 (Fig. 110G) represented by 3 equal setae on genital operculum.

Male. Unknown.

Remarks. Although Goniodelphys nosybensis sp. nov. does not have the typical body form of the genus, its fourth pedigerous somite is fusedto the fifth and forms the brood pouch which is tapering and extended posteriorly, and the free urosome is inserted somewhat anteriorly into the ventral side of the brood pouch. Legs 2–4 have 3-segmented rami and each leg has 2 inner setae on the second endopodal segment. On the basisof thesecharacter states, the new species is placed in Goniodelphys.

The possession of 5 setae on the first endopodal segment of the mandible of G. nosybensis sp. nov. is an extraordinary feature, unique within the Notodelphyidae: the maximum setation for this segment reported elsewhere in the family is 4 setae. The presence of armature on the female leg 6 (represented by 3 setae on the genital operculum) isalsoanunusual feature.Thesecharacteristics serve to distinguish the new species from its congeners.