Notopygus, 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 : 391

Notopygus gen. nov.

Diagnosis. Body of female inflated; prosome bulbous, indistinctly segmented. Brood pouch occupying most of metasome. Free urosome 5-segmented in female and 6-segmented in male. Caudalramus with 6 armature elements, at least one transformed to spine. Antennule 9- or 10-segmentedwith 3 setaeonfirst segment. Antenna 4-segmented including coxa, basis, and 2-segmented endopod; exopod reduced to small knob with minute setal vestiges, or absent. Mandible consistingof coxa, basis, exopod, and endopod; exopod armedwith 4 large setae, and endopod with 4 and 10 setae on first and second segments, respectively. Maxillule armed with 9 setae on arthrite, 1 on coxal endite, 2 on epipodite, and 3 on each basis and endopod; exopod with 3 setae and additional setal vestige. Maxilla with well-developed claw on basis. Maxilliped obscurely 2-segmented with 9 setae on first segment and 2 setaeon second. Leg 1 with 3-segmented exopod and 2- or 3-segmented endopod; outer seta on basis smallas inlegs 2–4. Legs 2–4 each with 3-segmented exopod and 2-segmented endopod; exopods bearing setae or setiform spines as outer armature elements. Third exopodal segment of leg 4 armed with 9 elements as in legs 2 and 3. Armature formula for legs 1–4 as follows:

Leg 5 consisting of protopod fused with pedigerous somite and free exopod armed with 1 spine and 1 seta distally.

Etymology. From Greek noto (“southern”) and pygus, the ending of many genera in the Notodelphyidae . It alludes to the South African distribution of the three known species of the genus. Gender masculine.

Type species. Notopygus unispinatus gen. et sp. nov. by original designation.

Other included species. Notopygus trispinatus gen. etsp. nov. and N. minutispinatus gen. etsp. nov.

Remarks. Notopygus gen. nov. can be separated from the closely related genus Doropygus by three main characters states: (1) one or more of the setal elements on the caudal ramus is transformed into a spine; (2) the metasome is swollen and bulbous; and (3) the third exopodal segment of leg 4 bears a total of 9 (rather than 8) armature elements. The last of these character states appears to be plesiomorphic relative to the state exhibited in Doropygus species.