Dimorphipodia, Lee & Huys, 2019

GENUS DIMORPHIPODIA View in CoL GEN. NOV.

u r n: l s i d: z o o b a n k. o r g: a c t: 3 2 2 B 9 7 1 F - B 3 5 7 - 4AA4-A6E1-CB4CE2496329

Diagnosis: Ancorabolinae . Body cylindrical, tapering slightly posteriorly, without clear demarcation between prosome and urosome. Urosomites without paired processes or tubercles. Cephalothorax with large, conical frontolateral horns; posterior margin without paired laterodorsal processes; lateroventral margin forming setulose lobate outgrowth. Somites bearing P2–P4, each with paired dorsal processes which are distinctly smaller in ♂; none of the thoracic processes dendroid; pleural areas with setular tufts. Genital somite (anterior half of genital double-somite in ♀) with lateral bulbous projections.Ventral posterior margins of urosomites with very fine setular extensions. Body somites and caudal rami with conspicuous tube-pores dorsally and laterally. Anal operculum with fine setules. Caudal rami elongate and cylindrical, with seven setae; seta III pinnate. Sexual dimorphism in body size, antennule, P2–P4 exopods, P3 endopod, P5, P6, genital segmentation and degree of development of dorsal body processes .

Rostrum small, discernible in dorsal aspect; fused to cephalic shield; with paired plumose sensilla, membranous projections and long distinctive midventral tube-pore subapically. Antennule four-segmented in ♀, six-segmented and with one segment distal to geniculation in ♂; aesthetasc arising from segments 3 and 4 in ♀, segments 5 and 6 in ♂; segment 1 elongate and with long spinules along anterior margin. Antenna with allobasis showing partial suture halfway along outer margin, abexopodal margin with two setae of equal length; exopod entirely absent; free endopodal segment with three lateral and six distal elements. Mandible with robust coxa; palp one-segmented, uniramous with five setae (three endopodal, one basal and one exopodal). Maxillule with two elements on coxal endite; basis with four elements; exopod and endopod completely incorporated into basis, represented by two and three setae, respectively. Maxillary syncoxa with two well-developed endites, each with three elements; allobasis drawn out into claw with three accessory elements around its base; endopod minute, with two setae. Maxilliped subchelate, slender and elongate; syncoxa with one reduced seta; endopod drawn out into long, narrow, curved claw with one accessory seta.

P1–P4: Intercoxal sclerites wide and narrow; praecoxae well developed; coxae small, trapezoid; bases extremely transversely elongate. P1 endopod absent, original position indicated by slightly membranous area with small nodule; exopod two-segmented, exp-2 with four geniculate setae and one outer bipinnate seta. P2–P 4 ♀ with three-segmented exopods; endopods absent (P2) or two-segmented (P3–P4); without inner setae on exp-1 and endopodal segments; exp-3 with only two outer spines. P2–P4 exp- 2 ♂ inner seta much longer than in ♀. Exp- 3 ♂ with one (P2, P4) or two (P3) inner setae; apical elements longer than in ♀. P3 endopod ♂ three-segmented; enp-2 elongate, anterior surface produced distally into recurved apophysis; enp-3 with two apical setae. Armature formula as follows:

P5 uniramous in both sexes; basal setophore reduced to short cylindrical outgrowth; endopodal lobe vestigial, represented by two minute setae and one (♀) or two (♂) conspicuous tube-pores; exopod elongate, with one inner, one apical and three outer elements (middle outer spine shortest and displaced to posterior surface), fused with baseoendopod in ♀, distinct in ♂. Female genital field located anteriorly, with moderately large copulatory pore; gonopores covered by common genital operculum derived from medially fused P6 with one naked seta on either side. Male P6 asymmetrical; without armature; functional member represented by small membranous flap.

Type and only species: Dimorphipodia changi

Etymology: The generic name is derived from the Greek δις (dis, twice), μορφή (morphe, form) and πους (pous, foot) and refers to the sexual dimorphism expressed on the exopods of each of the swimming legs (P2–P4). Gender: feminine.