Semicytherura parva, Luz & Coimbra, 2022

Luz, Nathália Carvalho Da & Coimbra, João Carlos, 2022, Ostracods (Crustacea: Ostracoda) of the Vitoria-Trindade Chain, Southwestern Atlantic, Zootaxa 5188 (4), pp. 301-329 : 307-308

Semicytherura parva sp. nov.

Fig. 3 : 10–16

Type series. Holotype: MP-O-2825, female, RV, length: 0.317 mm, height: 0.179 mm . Paratypes: MP-O-2826, female, LV, length: 0.321 mm, height: 0.177 mm; MP-O-2827, male, RV, length: 0.299 mm, height: 0.177 mm; MP- O-2828, male, LV, length: 0.304 mm, height: 0.169 mm .

Type locality. Davis Seamount, Sample M11008 D.

Etymology. Latin origin, parvus = small, regarding the small size of the species.

Material. Dead assemblage: 7 RV, 14 LV, and 1 juvenile . Living assemblage: 2 adults.

Diagnosis. Carapace very small; dorsal margin evenly convex in RV, almost straight in LV. Caudal process middorsal, more acute in RV. Eye tubercle weak. Surface strongly reticulate, with well-marked longitudinal ridges, one of which surrounds the ventrolateral alar process, terminating thicker and more sinuous in RV. Reticules ornamented by numerous small punctae.

Description. Carapace very small, thick-shelled, subrectangular to subovate in lateral view, flattened ventrally. In dorsal view, subovate with greater width in the ventrolateral alar processes. Valves unequal, RV overlapping LV mainly dorsally. RV greatest height medianly, LV greatest height just behind mid-length. Dorsal margin evenly convex in RV, subrectilinear in LV. Ventral margin with a gentle oral concavity, partially obscured by a ventrolateral alar process. Anterior margin more rounded in the upper half, in RV; less protruded in LV. A very delicate concavity marks the contact between the anterior and ventral margins. Posterior margin with a well-developed mid-dorsal caudal process, more acute in RV. Ornament strongly reticulate over the entire surface, with well-marked longitudinal ridges, one of which surrounds the ventrolateral alar process, terminating thicker and more sinuous in RV. Reticules ornate by numerous small punctae. Eye tubercle weak. Hinge as for genus, RV with bilobate anterior tooth, smooth median groove, and a small rounded posterior tooth connected to an elongate bar. Inner lamella quite wide anteriorly and posteriorly. Sexual dimorphism typical for the genus.

Remarks. Semicytherura parva sp. nov. resembles Semicytherura bertelsae Coimbra et al., 1999b but differs by the smaller size, the convex RV dorsal margin, and more dorsally positioned caudal process. The number and the distribution pattern of reticules and longitudinal ridges are distinct in both species.

Stratigraphic range. Holocene.

Occurrence and distribution. Davis seamount ( Tab. 4 ).

Figures

FIGURE 3. 1–2: Hemicytherura bradyi. 1) MP-O-2820, RV; 2) MP-O-2821, LV. 3–9: Hemicytherura trindadensis sp. nov. 3) MP-O-2822, RV, holotype; 4) MP-O-2822, LV, paratype; 5) MP-O-2823, RV, paratype; 6) MP-O-2823, LV, paratype; 7) MP- O-2823, RV, paratype, internal view; 8) MP-O-2823, LV, paratype, internal view; 9) MP-O-2824, paratype, dorsal view. 10–16: Semicytherura parva sp. nov. 10) MP-O-2825, female, RV, holotype.; 11) MP-O-2826, female, LV, paratype; 12) MP-O-2827, male, RV, paratype; 13) MP-O-2828, male, LV, paratype; 14) MP-O-2827, male, RV, paratype, internal view; 15) MP-O-2828, male, LV, paratype, internal view; 16) MP-O-2825, female, RV, paratype, hinge. 17–18: Semicytherura sp. 17) MP-O-2830, RV; 18) MP-O-2830, LV. 19–20: Callistocythere cranekeyensis. 19) MP-O-2818, carapace, RV; 20) MP-O-2819, carapace, LV. 21–22: Loxoconcha forda. 21) MP-O-2831, RV; 22) MP-O-2832, LV. 23–24: Loxoconcha foveata. 23) MP-O-2833, female, RV; 24) MP-O-2834, female, LV. Scale bar: 100 µm.