Ammonixys, Kim & Boxshall, 2020

Kim, Il-Hoi & Boxshall, Geoff A., 2020, Untold diversity: the astonishing species richness of the Notodelphyidae (Copepoda: Cyclopoida), a family of symbiotic copepods associated with ascidians (Tunicata), Megataxa 4 (1), pp. 1-6 : 539

Ammonixys gen. nov.

Diagnosis. Body globular with swollen, almost spherical, fourthpedigerous somite. Freeurosome 5-segmented. Caudalsetae obscure. Rostrum well-developed.Antennule small, 6-segmented. Antenna 4-segmented withsmall terminal claw. Mandible with 4 teeth on coxal gnathobase; exopod fused with basis, represented by 2 setae; endopod 2-segmented with 1 and 4 setae on first and second segments, respectively. Maxillulewith 6 setaeon arthrite, 1 each on coxal epipodite and basis, 4 on exopod and 3 on endopod; coxal endite absent. Maxilla 4-segmented; syncoxa with 2 endites; basis with claw plus 1 seta; endopod 2-segmented. Maxilliped as unsegmented lobe bearing 4 setae. Legs 1–3 with 3-segmented rami. Leg 4 with 3-segmented exopod and 2-segmented endopod. Innercoxalsetaabsentinlegs 1–4. Leg 1 lacking inner distal element on basis. First and second exopodal segments of legs 1–4 lacking inner seta. First and second endopodal segments of legs 1–3 lacking inner seta. Leg 5 represented by lobe and tapering, sclerotized process located ventrodistally on somite.

Typespecies. Ammonixysquadridens gen. etsp. nov. by original designation.

Etymology. The name is derived from the Greek ammon (=African) and ixys, referring to the discovery of the new genus in Africa.

Remarks. Ammonixys gen. nov. resembles Doroixys in the absence of the inner seta on the proximal endopodal segment(s) of legs 2–4, but the new genus exhibits a striking derived feature separating it from Doroixys and other genera, namely, the loss of a distinct mandibular exopod. The exopod is respresented only by a pair of setae originating on the surface of the fused basis plus exopod. The setation of leg 1 is also distinctive because the first and second exopodal and endopodal segments of leg 1 all lack an inner seta, and the basis of leg 1 is unarmed. This setation of leg 1 differs from that expressed by the four new genera described above, Prodoroixys gen. nov., Notoixys gen. nov., Borixys gen. nov., and Cystixys gen. nov. Although the loss of inner setae from the exopod of leg 1 occurs in Loboixys , the latter genus usually retains the inner setae on the endopod of leg 1. Unlike in Ammonixys gen. nov., the seven known species of Loboixys each have a 3-segmented antenna and carry 6 setae on the maxilliped. This constitutes an additional significant difference between Loboixys and Ammonixys gen. nov., which has a 4-segmented antenna and carries only 4 setae on the maxilliped.