Sipadantonius, Boonyanusith & Wongkamhaeng & Azman, 2024

Boonyanusith, Chaichat, Wongkamhaeng, Koraon & Azman, Abdul-Rahim, 2024, Sipadantonius roihani gen. et sp. nov., a new genus and species of Pseudocyclopidae Giesbrecht, 1893 (Copepoda, Calanoida) from the marine cave “ Turtle Tomb ” of Sipadan Island, Sabah, Malaysia, ZooKeys 1219, pp. 303-329 : 303-329

Genus Sipadantonius gen. nov.

Diagnosis.

Female: Elliptical body. Single plate rostrum, with rounded tip, lacking rostral filaments. Six-segmented prosome. Symmetrical and rounded postero-lateral corners of the fifth pedigerous somite. Four-segmented and symmetrical urosome. Double-somite genital with genital operculum ventromedially. Symmetry furcal rami, with serrated hyaline frill on distal margin, armed with five setae on the tip of the ramus, without furcal setae I and III; spiniform seta II; normal-developed seta V, slightly longer than seta IV. Antennule with 26 segments-; ancestral segments II and fused III; ancestral segments X and partly fused XI; relatively short ancestral segment XXVII; with aesthetasc on ancestral segments I, III – XXI, XXV, and XXVII. Antennae with two-segmented Endp and nine-segmented Exp; segments I – VII of Exp each with one seta. Mandibles with un-modified coxal gnathobase, five-segmented Exp and two-segmented Endp; a distal segment of Endp with ten setae. Maxillulae with nine setae on coxal epipodite and six setae on coxal endite; unarmed basal exite; two-segmented, un-modified Endp. Seven-segmented maxillae lack an outer seta on the outer margin of the coxa. Eight-segmented maxillipeds; length of segments II – VI of Endp is equivalent to syncoxa; transformed proximalmost seta on segment III, with feather-like tip. Three-segmented P 1 – P 5 with both rami; coxa with seta on the distomedial corner; the basis of all swimming legs lacking lateral seta, that of P 2 – P 5 with cuticular window representing the remnant of armament on outer margin; the posterior surface of the basis of P 1 with the curved hyaline process. Spine and setal complements of Exp - 3 of P 2 – P 5: 2.3.3.3 and 5.5.5.4, respectively; setal complement of Endp - 3 of P 2 – P 5: 8.7.7.6. Distolateral corner of P 1 Endp- 1 and Endp - 2 of P 1 – P 4 with bifid indentures; distolateral corner of both Endp- 1 and Endp - 2 of P 5 un-fid. Male: Body shape, rostrum, prosome, mouthparts, furcal rami, and P 1 – P 4 are identical to those of females. Slightly asymmetrical urosome. The left antennule is identical to that of the female; the 22 - segmented right antennule, weakly geniculate; fused ancestral segments II – IV, XXI – XXIII, and XXIV – XXV. P 5 is asymmetrical, with both three-segmented rami; basis with cuticular pores representing the remnant of armament on outer margin; Endp- 1 of left and right legs lacks inner seta; separated Exp - 2 and Exp - 3; those of the right leg are modified to function as grasping organ.

Type species.

Sipadantonius roihani sp. nov.

Etymology.

Named after the type locality, Sipadan Island, Sabah, Malaysia, in combination with the - tonius stem from the existing generic name Pinkertonius Bradford-Grieve, Boxshall & Blanco-Bercial, 2014 , alluding to the similarity of the genus Pinkertonius . The gender is masculine.