Phlyctocythere christophei, 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 : 312

Phlyctocythere christophei sp. nov.

Fig. 4 : 11–15

1999a Phlyctocythere sp. 1 Coimbra et al., p. 368, pl. 1, fig. 9, tab. 1.

Type series. Holotype: MP-O-2839, RV, length: 0,460 mm, height: 0,297 mm . Paratype: MP-O-2840, LV, length: 0.425 mm, height: 0.280 mm.

Type locality. Vitoria Seamount, Sample M11001 D.

Etymology. In honor of Jean-Christophe Joyeux who kindly provided the samples from the seamounts.

Material. 3 RV, 2 LV, and 2 juveniles (dead assemblage) .

Diagnosis. A small, clearly inequivalve, and irregularly ovate species of Phlyctocythere . RV dorsal margin anteriorly convex and somewhat concave posteriorly; in LV less arched, slightly sinuous posteriorly. Two (RV) or three (LV) concentric wrinkles runs subparallel to the ventro-posterior and posterior margins, finishing before reaching the caudal process. Eye tubercle rather faint, anterodorsally.

Description. Carapace small, clearly inequivalve, thin-shelled, fragile, and irregularly ovate in lateral view. Maximum height just in front of the middle; maximum length subdorsal; maximum width near the middle. Valves strongly inflated, with a compressed peripheral zone similar to a very delicate flange anteriorly, large and similar to a sharp keel ventro-posteriorly and posteriorly. Eye tubercle rather faint, anterodorsally. Anterior margin almost evenly rounded. Posterior end rather blunt, with an obtuse subdorsal caudal process. Ventral margin sinuous. Dorsal margin anteriorly convex and somewhat concave posteriorly, in RV; almost straight but slightly sinuous posteriorly, in LV. Surface smooth, except for a few wrinkles. Two (RV) or three (LV) concentric wrinkles runs subparallel to the ventro-posterior and posterior margins, finishing before reaching the caudal process. Inner lamella broad, except in the oral region. Anterior vestibule wide; posterior vestibule narrow. Hinge consists of a fine and smooth bar in RV and a corresponding groove in LV. Adductor muscle scars aligned in a slightly curved row of four compact scars; frontal scar poorly visible, somewhat U-shaped.

Remarks. Phlyctocythere christophei sp. nov. is an exceedingly rare species, previously recorded in open nomenclature on the Brazilian equatorial shelf by Coimbra et al. (1999a). It resembles the Caribbean Miocene species Phlyctocythere curva Bold, 1988 , differing mainly by the more elongate outline, less arched dorsal margin, absence of anterior faint reticulae and RV with only two ventro-posterior and posterior concentric wrinkles. P. christophei sp. nov. is very similar to P. apua sp. nov., diverging in the less spherical outline in lateral view, number and distribution of wrinkles, and a hinge lacking traces of terminal elements. Similar to other species attributed to the genus, all specimens of P. christophei sp. nov. have the posterior margin and the caudal process somewhat damaged.

Stratigraphic range. Holocene.

Occurrence and distribution. In the study area: Vitoria and Davis seamounts ( Tab. 4 ). Also occurs in the Brazilian Northern shelf, from Orange Cape to the mouth of Pará River (see references in the synonymy list).

Figures

FIGURE 4. 1–10: Loxocorniculum micropapillosum sp. nov. 1) MP-O-2836, female, RV; 2) MP-O-2835, female, LV, holotype; 3) MP-O-2837, male, RV, paratype; 4) MP-O-2837, male, RV, paratype, papillae detail. 5) MP-O-2837, male, RV, paratype, internal view; 6) MP-O-2835, female, LV, holotype, internal view; 7) MP-O-2837, male, RV, paratype, hinge; 8) MP- O-2835, female, LV, holotype, hinge; 9) MP-O-2837, male, RV, paratype, central muscle scars; 10) MP-O-2838, juvenile, RV, paratype, sieve-type normal pore canal. 11–15: Phlyctocythere christophei sp. nov. 11) MP-O-2839, RV, holotype; 12) MP-O- 2840, LV, paratype; 13) MP-O-2839, RV, holotype, internal view; 14) MP-O-2840, LV, paratype, internal view. 15) MP-O-2840, LV, paratype, central muscle scars. 16–20: Phlyctocythere apua sp. nov. 16) MP-O-2841, RV, holotype; 17) MP-O-2842, LV, paratype; 18) MP-O-2841, RV, holotype, internal view; 19) MP-O-2842, LV, paratype, internal view; 20) MP-O-2842, LV, paratype, central muscle scars. 21–22: Kotoracythere inconspicua. 21) MP-O-2843, RV. 22) MP-O-2844, juvenile, LV. 23) Paracytheridea inflata, MP-O-2845, male, RV. 24–25: Paracytheridea tschoppi. 24) MP-O-2847, RV, female; 25) MP-O-2848, LV, female. Scale bar: 100 µm.