Untold diversity: the astonishing species richness of the Notodelphyidae (Copepoda: Cyclopoida), a family of symbiotic copepods associated with ascidians (Tunicata) Author Kim, Il-Hoi 0000-0002-7332-0043 Korea Institute of Coastal Ecology, Inc., 802 - ho, 302 - dong, 397 Seokcheon-ro, Ojeong-gu, Bucheon, Gyeonggi-do 14449, Republic of Korea ® ihkim @ gwnu. ac. kr; https: // orcid. org / 0000 - 0002 - 7332 - 0043 ihkim@gwnu.ac.kr Author Boxshall, Geoff A. 0000-0002-7332-0043 Korea Institute of Coastal Ecology, Inc., 802 - ho, 302 - dong, 397 Seokcheon-ro, Ojeong-gu, Bucheon, Gyeonggi-do 14449, Republic of Korea ® ihkim @ gwnu. ac. kr; https: // orcid. org / 0000 - 0002 - 7332 - 0043 ihkim@gwnu.ac.kr text Megataxa 2020 2020-12-24 4 1 1 6 http://zoobank.org/3fdd970e-62f1-4f67-8cce-10870bdb3c01 journal article 54097 10.11646/megataxa.4.1.1 7c9bc39d-9910-46f1-9558-c0647b9cbbdb 2703-3090 4591138 Achelidelphys bifida sp. nov. ( Fig. 445 ) Typematerial . Holotype ♀ (intact, MNHN-IU-2014- 21471 ) from Didemnum poecilomorpha Monniot F & Monniot C, 1996 (Type MNHN-IT-2008-3239 = MNHN A2/DID.C/230), CRRFOCDN 1379-J, north of Sulawesi , Indonesia (0l°51.52’N, 125°03.84’E ), depth 40 m , 20 May 1993 . Etymology . The species name refers to the biramous leg 4 of the new species Description of female . Body ( Fig. 445A, B ) unsegmented, stellate. Body length 2.20 mm measured from anterior margin of cephalosome to distal tip of urosome. Greatest width 1.95 mm between lateral tips of leg 2 exopods. Body surface ornamented with minute setules ( Fig. 445C ). Urosome ( Fig. 445C ) present as small lobe at posterior end of body, fused with prosome, bearing 2 small, unequal lobes (probably caudal rami) at posterior margin; caudal setae absent. Rostrum ( Fig. 445B ) positioned on ventral surface of cephalosome, digitiform, anteroventrally-directed, tapering, about 3 timeslongerthan wide. Antennules ( Fig. 445A, B ) as paired tapering anterolateral processes on cephalosome, each with dorsally curved tip. Antennae absent. Labrum ( Fig. 445B ) as globular, ventrally-directed lobe, positioned between leg 1 pair. Mouthparts absent. Legs 1–4 biramous ( Fig. 445B ). Rami of leg 1 subequalin length; exopod directed laterally, curved, slightly broader than endopod; endopod directed ventrally and curved anteriorly. Exopods of legs 2–4 broader than thatofleg 1, tapering, abouttwiceaslongas wide.Exopods of legs 2 and 3 laterally-directed and curved posteriorly. Exopod of leg 4 posteromedially-directed. Endopods of legs 2–4 shorter and narrower than exopods, digitiform, about 3 times longer than wide, laterally-directed in legs 2 and 3, but posteriorly-directed in leg 4. Digitiform midventral processes present between leg pairs 2 and 3 ( Fig. 445B ). Leg 5 absent. Male . Unknown. Remarks . With laterally-directed legs 1–4 and a metasome not extending beyond the insertion of leg 4, the new species belongs to the genus Achelidelphys , as defined by Boxshall & Marchenkov (2007) . Within the genus, A . bifida sp. nov. is most closely related to A . steinitzi Lafargue & Laubier, 1977 in having two median ventral processes, one between leg 2 pair and the other between leg 3 pair. However, A . bifida sp. nov. can be differentiated from A . steinitzi and other congeners by the biramous condition of leg 4. Within the Brementia - group of notodelphyids, a biramous leg 4 was previously recordedin the genera Brementia and Pholeterides , as well as in three species of Anoplodelphys ( A . corneci Lafargue & Laubier, 1978 , A . galli Lafargue & Laubier, 1978 , and A . incerta Lafargue & Laubier, 1978 ). However, all these species possess paired antennae, which are lacking in A . bifida sp. nov.