Bathynotodelphys, 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 : 8-9

Bathynotodelphys gen. nov.

Diagnosis. Female body bilaterally compressed with internal brood pouch extending from anterior margin of fourth pedigerous somite backwards, out over anterior half of urosome. Fifth pedigerous somite incorporated into brood pouch of female. Free urosome 5-segmented in female consisting of genital somite and 4 abdominal somites; 6-segmented in male. Rostrum well-developed, plate-like. Female antennule 9-segmented: segmental fusion pattern I-II, III-XI, XII-XIV, XV-XVI, XVII-XX, XXI-XXIII, XXIV, XXV, XXVI-XXVIII. Male antennule 10-segmented; non-geniculate, segmental fusion pattern I-II, III-XI, XII, XIII, XIV, XV-XVI, XVII, XVIII-XX, XXI-XXIII, XXIV-XXVIII. Antenna consistingof coxa, basis, and 3-segmented endopod bearing terminal claw; exopod represented by 1 large and 1 minute seta. Mandible with well developed coxalgnathobase and biramous palp armedwith 1 setaon basis, 5 setaeon exopod, and 4 and 10 setae on first and second segments, respectively. Maxillule with 9 setae on arthrite, 1 on coxal endite, 2 on epipodite, and 3 onmedial margin of basis; exopod unsegmented with 4 setae distally; endopod 2-segmented with 2 or 3 setaeon first segment and 4 setae on second. Maxilla indistinctly 6-segmented, but with precoxa and coxa separated by incomplete suture; enditic formula 4, 1, 2, 3; basiswith clawplus 2 setae; 3-segmented endopod with setal formula 1, 1, 4. Maxilliped 3-segmented and armed with 9 or 10 setae on first segment, 1 on second and 4 on third. Legs 1–4 biramous with 3-segmented rami; armatureformula:

Coxa Basis Exopod Endopod
Leg 1	0-1	1-I	I-1; I-1; III, I, 40-1; 0-1; 1, 2,3
Legs 2 & 30-1		1-0	I-1; I-1; III, I, 50-1; 0-2; 1, 2, 3
Leg 4	0-1	1-0	I-1; I-1; II, I, 5 0-1; 0-2; 1, 2, 2

Leg 5 consisting of protopod fused with somite and well-developed free exopodal segment armed with 2 elements (1 spineand 1 seta).

Type species. Bathynotodelphys defayeae gen. et sp. nov. by original designation.

Etymology. The generic name is a combination of Bath - (”deep” in Greek) and the existing generic name Notodelphys . It refers to the deep-water habitat of the new genus.

Remarks. This new genus exhibits numerous plesiomorphies, many of which are shared with the genus Archinotodelphys Lang, 1949 . However, in possessing an internal brood pouch in the female and a free exopod of leg 5 armed with only 2 armature elements, the new genus cannot be placed in the family Archinotodelphyidae . Its affinities lie more strongly with the Notodelphyidae . The new genus shares many similarities with the type genus Notodelphys Allman, 1847 , but the retention of a 3- segmented endopod of the antenna is a major difference, since species of Notodelphys are characterised by a 2- segmentedendopodinwhich theancestralsecondandthird endopodal segments are fused to form a compound distal segment. This is a significant difference which supports the establishment of the new genus to accommodate B. defayeae gen. etsp. nov., describedbelow.Theincomplete fusion of the precoxa and coxa of the maxilla, as exhibited by the new species, is an additional plesiomorphic state relative to that exhibited by species of Notodelphys which is characterised by the fusion of the precoxa and coxa of the maxilla to form a syncoxa.