Nodoscarus, 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 : 631-633

Nodoscarus gen. nov.

Diagnosis. Body elongate, vermiform, cylindrical, and unsegmented. Cephalosome not defined from metasome or obscurely defined from metasome by constriction. Urosome also not defined from metasome or defined from metasome by rudimentary dorsal suture line. Body surface usually covered with minute setules. Caudal rami rudimentary or absent. Rostrum present, usually large or rostrum absent. Antennule short, unsegmented or with traces of articulations. Antenna 3-segmented, comprising coxa, basis, and unsegmented endopod bearing small terminal claw. Labrum present, notcovering oral appendages. Two or 3 pairs of mouthparts present. Mandible lacking coxa, represented only by lobate or biramous palp. Maxillule as unsegmented, setiferous lobe. Maxilla present or absent, if present, 1- to 3-segmented. Maxilliped and legs absent.

Type species. Nodoscarus bretoni gen. et sp. nov. by original designation.

Other included species. Nodoscarus dakarensis gen. etsp. nov., N. compressus gen. etsp. nov., N. curvus gen. etsp. nov., N. latirostris gen. etsp. nov., N. scutatus gen. etsp. nov., N. rectus gen. etsp. nov., N. senisetatus gen. etsp. nov., and N. quadrisetatus gen. et sp. nov.

Etymology. The name is derived from the Greek nod (=toothless) and scari (=a little worm) and refers to the absence of a coxa on the mandible. Gender masculine.

Remarks. Nodoscarus gen. nov. can readily be distinguished from thegenera Pythodelphys and Lissodelphys gen. nov, which share the same derived body form, by the absence of the coxa on the mandible.

In the genus Pythodelphys , the type species, P. acruris Dudley & Solomon, 1966, has a coxa on the mandible ( Dudley & Solomon, 1966). Its only congener, Pythodelphys illgi Ooishi, 1998 , lacks a mandibular coxa according to the original description (Ooishi, 1998). If Ooishi’sobservationiscorrect, P. illgi shouldbetransferred to Nodoscarus gen. nov. However, inasmuch as P. illgi is so similar to P. acruris in respect of the morphology of the other appendages that we propose to tentatively retain P. illgi in Pythodelphys until the morphology of its mandible can be confirmed. The mandibular coxa of these vermiform notodelphyids is very easy to overlook due to its thinness and transparency.

Unlike Lissodelphys gen. nov., the new genus Nodoscarus gen. nov. lacks maxillipeds, and the setation of the mandible, maxillule and maxilla is generally much better developed in Nodoscarus gen. nov. than in Lissodelphys gen. nov.

Key to species of Nodoscarus gen. nov.

1. Three pairs of mouthparts present; maxillule (second pair) armed with more than 2 setae........................................... 2

Only 2 pairs of mouthparts present: maxillule armed with 2 setae .................................................................................. 8

2. Maxillule armed with fewer than 8 setae; maxilla 1- or 2- segmented, with fewer than 7 setae.................................. 3

Maxillule armed with more than 8 setae; maxilla 3- segmented armed with 7 or more setae ............................ 4

3. Mandible, maxillule, and maxilla armed with 5, 7, and 6 setae, respectively ............... N. dakarensis gen. etsp. nov.

Mandible, maxillule, and maxilla armed with 1, 6, and 2 setae, respectively.............. N. compressus gen. etsp. nov.

4. Maxilla with 2 setae on first segment (syncoxa) .............. 5

Maxilla with 4 setae on first segment (syncoxa) .............. 6

5. Mandible with 7 setae; maxilla armed with 1 and 4 setae on second and third segments, respectively ............................ ................................................... N. curvus gen. etsp. nov.

Mandible with 9 setae; maxilla armed with 2 and 3 setae on second and third segments, respectively ............................ .............................................. N. latirostris gen. etsp. nov.

6. Caudal rami absent; mandible with total of 10 setae .......... .................................................. N. bretoni gen. etsp. nov.

Small caudal rami present; mandible with 9 setae ........... 7

7. Mandible biramous; rostrum narrowing in proximal third, widest in middle, and tapering along distal two-thirds....... ................................................ N. scutatus gen. etsp. nov.

Mandible uniramous; rostrum widest at proximal 40%, abruptly narrowing and tapering in distal 60% .................. .................................................... N. rectus gen. etsp. nov.

8. Rostrum well-developed; mandible with 6 setae................ ............................................ N. senisetatus gen. etsp. nov.

Rostrum absent; mandible with 4 setae .............................. ........................................ N. quadrisetatus gen. etsp. nov.