Loxocorniculum micropapillosum, 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 : 310-311

Loxocorniculum micropapillosum sp. nov.

Fig. 4 : 1–10

2020 Loxocorniculum sp. Machado et al., p. 9, fig. 6C; p. 16, tab. 1.

Type series. Holotype: MP-O-2835, female, LV, length: 0.506 mm, height: 0.311 mm. Paratypes: MP-O-2836, female, RV, length: 0.536 mm, height: 0.311 mm; MP-O-2837, male, RV, length: 0.517 mm, height: 0.273 mm; MP- O-2838, juvenile, RV, length: 0.428 mm, height: 0.241 mm .

Type locality. Vitoria Seamount, Sample M11001 D.

Etymology. Regarding the small papillae that ornament both muri and the peripheral zone adjacent to the free margin.

Material. 2 RV, 2 LV, and 1 juvenile (dead assemblage) .

Diagnosis. A medium, thick-shelled, and strongly ornamented species of Loxocorniculum . Eye tubercle large and rounded. Ornamentation with coarse reticulae, fossae varying in shape and size, and predominantly longitudinal ridges. Small papillae cover most muri and the compressed peripheral zone.

Description. Medium-sized carapace, heavily calcified, subrectangular to subquadrate, peripherally compressed in lateral view. Greatest height and width posteriorly. Dorsal margin straight but appearing somewhat sinuous due to the over-reach of the dorsal ornaments; posteriorly hidden by a horn-like tubercle. Ventral margin with a gentle oral concavity, obscured by the submarginal ornamentation; an ornate flange protrudes in the posterior half.Anterior margin slightly concave in upper 1/3, rounded in lower 2/3; three narrow elongated fossae adorn the anteromedian margin. Posterior margin with a small, blunt dorsal caudal process. Eye-tubercle rounded and prominent. Surface ornamented by coarse reticulae with fossae varying in shape and size, and predominantly longitudinal ridges. Delicate and numerous papillae cover most muri and the compressed peripheral zone. Two well-developed horizontal anteromedian ridges, typical for the genus, delimit three papillate huge submarginal fossae. The upper anteromedian ridge runs to the center, turns up, and subdivides into two branches, one reaching the ocular tubercle and another following backward by a short distance and then upwards reaching the horn-like tubercle. The lower anteromedian ridge runs back to the posterior ventrolateral tubercle and turns up raising a short vertical ridge that subdivides into two branches, the most robust follows to the center, the most delicate follows obliquely backward and upwards and splits becoming Y-shaped. Three subparallel horizontal ridges run in the anterior ventrolateral half. The uppermost reaches the posteroventral alar tubercle, folds obliquely up and backward, and follows very sinuously to the posterodorsal horn-like tubercle. RV with two small projections behind the posteroventral alar tubercle but only one in LV. A sinuous dorsal ridge begins in the eye tubercle and runs backward reaching the posterodorsal horn-like tubercle. Normal porecanals not numerous, sieve-type. Hinge gongylodont with somewhat atypical anterior and anteromedian elements. Anterior and posterior inner lamella moderately wide. Central muscle scars four adductors in a sub-vertical row, a C-shaped, anteriorly opened frontal scar, and two mandibular scars. Sexual dimorphism distinct: males more elongate, with inconspicuous lateral tubercles, and a longer and narrower posteroventral flange.

Remarks. Loxocorniculum micropapillosum sp.nov. is easily distinguished from other species of Loxocorniculum mainly by its strong reticulae with fossae varying in shape and size and the muri covered by small papillae that also adorn the wide compressed peripheral zone.

Stratigraphic range. Holocene.

Occurrence and distribution. In the study area: Vitoria and Davis seamounts ( Tab. 4 ). Also occurs in the Brazilian Northeastern shelf (Lat. 07°45’- 08°03.5’S, Long. 34°31- 34°36’W) (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.