Ctenixys, 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 : 542-544

Ctenixys gen. nov.

Diagnosis. Body inflated. Dorsal cephalic shield well defined from metasome, with or without paired posterolateral horn-like processes. Metasome unsegmented, longer than wide, gradually broadening posteriorly. Freeurosome 5-segmented. Caudalramus small; caudal setae obscure or absent. Rostrum present. Antennule 6- or 7-segmented; setae small, not discernible from setules. Labrum weak. Mandible consistingof coxa with straight, pectinate medial margin, and palp comprising basis bearing 1 seta, exopod bearing 5 setae, and 2-segmented endopod bearing 1 and 4 setae on first and second segments, respectively. Maxillule with 3 or 4 setae on arthrite, 1 on coxal epipodite; coxal endite absent; exopod and endopod fused with basis, with 7 or 8 setae (3 or 4 on exopodal region, 3 on endopodal region, and 1 on basis region). Maxilla 3-segmented; syncoxa with 3 endites; basis with strong claw only; endopod unsegmented, armed with 3 setae. Maxilliped as small lobe bearing 4 to 8 setae. Swimming legs with reduced segmentation and setation; inner coxal seta absent. Leg 1 with 1- or 2-segmented rami; inner distal seta of basis present or absent. Legs 2–4 each with indistinctly 2- segmented exopod; endopod absent or represented by small knob. Leg 5 vestigial or represented by 2 small lobes.

Type species. Ctenixys pusilla gen. et sp. nov. by original designation.

Other included species. Ctenixys abdominalis ( Stock, 1967) comb. nov. (originally as Demoixys abdominalis ) and C. affinis ( Stock & Humes, 1970) comb. nov. (originally as Demoixys affinis ).

Etymology. The generic name is the combination of the Greek cten (=comb) and ixys, the ending of many generic names in the family Notodelphyidae . It alludes to the comb-like medial margin on the coxal gnathobase of the mandible.

Remarks. Demoixys abdominalis Stock, 1967 and D. affinis Stock & Humes, 1970 are here transferred into Ctenixys gen. nov. The significant synapomorphy shared by all speciesof the new genus is the pectinate medial margin of the coxal gnathobase of the mandible. This form of coxal gnathobase, which lacks defined teeth on the medial margin, is distinctly different from that of Demoixys which bears between 3 and 5 teeth.