Ammonixysquadridens gen. etsp. nov.

(Figs. 361, 362)

Type material. Holotype ♀ (dissected and mounted on a slide, MNHN-IU-2014-21404) from Polyclinum isipingense Sluiter, 1898 (MNHN-IT-2008-XXX = MNHN A1/POL.B/108), ATIMOVATAE TR07, Madagascar (25°01 Ś, 47°00 É), depth 12-16 m, MNHN coll., 01 May 2010.

Etymology. The specific name is from the Latin quadr (=four) and dens (=tooth), referring to the presence of four teeth on the coxal gnathobase of the mandible.

Descriptionoffemale. Body (Fig. 361A, B)globular, greatly swollen: body length 1.12 mm from frontal margin of cephalosome to posterior margin of fourth pedigerous somite. Prosome with smooth surface; lateral margins of dorsal cephalic shield expanded ventrally, completely concealing mouthparts in lateral view. Metasome 4- segmented; first and second articulations complete, third articulation incomplete; first to third pedigerous somites much wider than long, Fourth pedigerous somite greatly expanded, spherical, 785×774 μm. Freeurosome (Fig. 361C) small, stout, 5-segmented, inserted into ventral surface of brood pouch (Fig. 361B). All urosomites much widerthan long; 4 abdominal somitessparsely ornamented with minute spinules. Caudal ramus (Fig. 361C) small, lobate, slightly longerthan wide, not articulated from anal somite, bearing minute setules; caudal setae apparently absent.

Rostrum (Fig. 361E) distinct, slightly longerthan wide (84×72 μm), tapering to narrow apex. Antennule (Fig. 361F) archedposteriorly, 117 μmlong, 6-segmented; third and fourth segments articulated from each other only on one surface; first segment with 2 setae; setation of other segments obscure due to similarity with setules; third, fifth and terminal segments each bearing 1 small aesthetasc. Antenna (Fig. 361G) stout, 4-segmented; coxa, basis, and first endopodal segment unarmed; basis shorter than first endopodal segment; narrower second endopodal segment about 2.3 times longer than wide (41×18 μm) and as long as first segment: armed with 3 small setae plus small terminal claw, about one-third as long as second endopodal segment.

Labrum (Fig. 361H) simple, unornamented, with short,broadposteromedian lobe.Mandible (Fig.361I) with coxal gnathobase bearing 4 teeth on distal half of medial margin and pectinate proximal half of medial margin: palp consisting of basis and 2-segmented endopod; basis with 1 seta mediodistally; exopod completely fused with basis, represented by outer lobe of basis and pair of large setae at base of lobe; endopod 2-segmented, incompletely articulated from basis, with 1 broad seta on first segment and 4 setaeon second. Maxillule (Fig. 362A) armedwith 6 setae on arthrite, 1 on coxal epipodite, 1 on basis, 4 on exopod and 3 on endopod; coxal endite absent. Maxilla (Fig. 362B) 4-segmented; syncoxa bearing 2 endites, with 3 setae on first endite and 2 on second; basis with strong claw plus 1 seta; small endopod with 1 seta on first segment and 3 setaeon second. Maxilliped (Fig. 362C) as small lobe bearing 4 setae.

Legs 1–4 (Fig. 362 D-G) biramous with 3-segmented exopods; endopods 3-segmented inlegs 1–3, but 2- segmented in leg 4. Protopod 2-segmented in leg 1, but unsegmented in legs 2–4. Inner coxal seta absent in legs 1–4. Leg 1 lacking innerdistal element on basis. Outer seta on basis present only in leg 3. Endopod of leg 1 strongly curved inwards. First exopodal segment of legs 3 and 4 and second exopodal segment of legs 2 and 4 each bearing spiniform outer distal process. Outer setae on third exopodal segment of legs 2–4 vestigial. Armature formula for legs 1–4 as follows:

Leg 5 (Fig. 361C) consisting of outer lobe tipped with 1 small seta and inner, tapering, sclerotized process; left and right inner processes interconnected.

Male. Unknown.

Remarks.Itisnoteworthythat Ammonixysquadridens gen. et sp. nov. was extracted along with Doroixys obesa sp. nov. and two other species of copepods ( Scolecodes sp. and Haplostoma sp.), all from the same ascidian host.