Kyphocalanus, Markhaseva, Elena L. & Schulz, Knud, 2009

Markhaseva, Elena L. & Schulz, Knud, 2009, A new family and genus of calanoid copepods (Crustacea) from the abyss of the Atlantic Ocean, Zootaxa 2304, pp. 21-40 : 23-24

Genus Kyphocalanus gen. nov.

Diagnosis. Female. Cephalon in lateral view strongly bent anteriorly. Rostrum as two short, prong-like points. Cephalosome and first pedigerous somite and pedigerous somites 4 and 5 separate. Urosome very short comparatively, of 4 somites, genital-double somite being the largest. Antennule shorter than prosome. Basis, endopod segment 1 and exopod segment 1 of antenna without setae; endopod segment 2 with 3 or 4 setae on inner lobe; exopod segment 2 with 1 short seta. Mandibular gnathobase long and slender, with narrow cutting edge; basis of mandible with 2 setae, proximal seta with conspicuous thickening at one-third length; endopod segment 1 without setae, segment 2 with 9 setae; exopod 5-segmented with 1, 1, 1, 1, and 1 setae. Praecoxal endite of maxillule with 3 slender setae; proximal basal endite without setae; distal basal endite with 1 seta and separate from endopod bearing 5 setae. Praecoxal and coxal endites of maxilla usually with 2 slender setae each; basal endite with 1 strong spine; endopod with 8 long and thick worm-like sensory setae. Praecoxal lobes of maxilliped syncoxa with 1 thin, slender and comparably short worm-like sensory seta on proximal lobe and 2 thick and long worm-like setae on medial lobe; distal lobe without seta, setal formula 1,2,0; coxal endite with 1 slender seta. P4 coxa, basis, endopod, and exopod segment 1 with posterior surface spinulation or not. P5 3-segmented, exopod with 2 unequal spines (1 shorter, terminal and 1 longer, inner and subterminal spine).

Male. Unknown.

Etymology. From “kyphos” (Greek, meaning bent), refers to the pronounced and strongly bent cephalon, viewed laterally. This characterization is combined with the existing generic name Calanus . Gender masculine.

Type species: Kyphocalanus atlanticus sp. nov., by monotypy.

Remarks. Synapomorphies for the genus Kyphocalanus are the presence of a knife handle-like basal part of the proximal seta of the mandibular basis and the maxillule distal basal endite and endopod separate and the distal basal endite bearing 1 seta only (vs 2–6 setae in other Bradfordians).

In addition to the characters of the family, the new genus differs from the majority of other Bradfordian families/genera by the following derived characters: i) antenna basis without setae, shared with tharybid genus Brodskius Markhaseva & Ferrari, 2005 , contrasting the presence of 1–2 setae in other Bradfordians; ii) antenna endopod segment 1 without setae, shared with Pseudophaenna Sars, 1902 (genus of unclear familial position) and some species of the tharybid genus Undinella Sars, 1900 , and contrary to 1–2 setae in other Bradfordians; iii) antenna endopod segment 2 with fewer than 10 setae, shared with Pseudophaenna , but this segment with 11–15 setae in other Bradfordians; iv) maxillule proximal basal endite without setae, shared with Bradfordiella Andronov, 2007 (genus of unclear familial position), in contrast to the presence of 2–5 setae in other Bradfordians; v) maxilla proximal praecoxal endite with 2 setae, shared with Rostrocalanus and some species of Bradfordiella , but with 3–5 setae in other Bradfordians; vi) maxilla distal praecoxal endite and proximal coxal endite with 2 setae each, shared with some species of Bradfordiella , and contrary to 3 setae in other Bradfordians; vii) maxilla distal coxal endite with 2 setae, shared with Phaenna Claus, 1863 (family Phaennidae ), but with 3 setae in other Bradfordians; viii) maxilla proximal basal endite with 1 setal element, shared with Bradfordiella , but with 3–4 setal elements in other Bradfordians; ix) 1 seta on maxilliped coxal endite is shared with some species of Undinella and Bradfordiella , in contrast to presence of 2 or 3 setae in other Bradfordian genera.

The similar derived armament of some oral limbs of Kyphocalanus gen. nov. and Bradfordiella is assumed to have arisen in a parallel development and independently, and thus both genera are not considered to be closely related. This is corroborated by apomorphies not shared by Bradfordiella : i) praecoxal arthrite of maxillule with 3 setae (vs 9 in Bradfordiella ); ii) distal coxal endite of maxilla with 2 setae (vs 3 setae in Bradfordiella ); iii) maxilla distal basal endite plus endopod with 8 very long and thick, worm-like sensory setae, longer than all sclerotized setae of maxilla (vs only 6 short sensory setae of unclear morphology (Andronov 2007: 632) in Bradfordiella ).

In addition, the new genus does not share apomorphies of Bradfordiella : i) antennule of only 18 articulated segments (vs 24 in Kyphocalanus ); ii) mandibular basis lacking setae (viz. 2 setae in Kyphocalanus ); iii) maxillule with coxal and basal endites reduced (vs these endites well developed in Kyphocalanus ); v) maxilliped praecoxal endites of syncoxa lacking setae (with 1, 2, 0 setae in Kyphocalanus ).