Xestoleberis subtriangularis, Luz, Nathália Carvalho Da & Coimbra, João Carlos, 2015

Luz, Nathália Carvalho Da & Coimbra, João Carlos, 2015, The genus Xestoleberis (Ostracoda: Xestoleberididae) in the Northern, Northeastern and Eastern regions of the Brazilian continental shelf, Zootaxa 3974 (2), pp. 177-195 : 189-191

Xestoleberis subtriangularis sp. nov.

Fig. 5 : 1–11

Type series. Holotype: MP-O-1692 adult female, RV length 0.54 mm, height 0.35 mm. Paratypes, one adult male (MP-O-1693) and four adult females (MP-O-1694–MP-O-1697).

Type locality. REMAC /Leg 7—Sample 3767 (9°19.5’S / 35°03’W); depth: 44 m; sediment: biodetritical sand.

Etymology. With reference to the shape of carapace in lateral view.

Material. 38 adults and 68 juveniles.

Dimensions. See table 4.

Diagnosis. A medium-sized species of Xestoleberis . Carapace extremely tumid, sub-triangular in lateral view. LV overlapping RV at the anterior and posterior ends. A very small and inconspicuous, flange more developed in RV, runs along the antero- and posteroventral margins. Eye-spot conspicuous and large, visible in transmitted light. Hinge antimerodont with median element coarsely crenulate. Adductor scars sub-elliptical and frontal spot somewhat rounded.

Description. A medium-sized and thick-shelled species of Xestoleberis . Sub-triangular in lateral view; subpiriform and strongly inflated in dorsal view. Ventral surface quite flattened. LV overlapping RV at the anterior and posterior ends. Maximum length in the lower third of the height. Maximum height almost in the middle. Maximum width at the posterior third. Anterior margin sloping obliquely anterodorsally and somewhat pointed anteroventrally. Posterior sub-truncated in RV and asymmetrically rounded in LV. Dorsal margin strongly arched. Ventral margin slightly convex. A very small and inconspicuous flange, more developed in RV, runs along the antero- and posteroventral margins. Surface typically smooth with two types of normal pore canals (sensu Sato & Kamiya 2007): sieve-type and lip-type. Eye-spot conspicuous and large, visible in transmitted light. Xestoleberis - spot long and narrow. Inner lamella relatively wide and with a well-defined anterior vestibulum; posterior vestibulum very narrow. Selvage peripheral, except ventrally. Marginal pore canals sparse, simple and straight. Hinge antimerodont with terminal teeth in RV and well-developed anterior element. Median element coarsely crenulate. Central muscle scars a vertical row of four sub-elliptical adductors; frontal scar somewhat rounded.

Sexual dimorphism present: male less flattened ventrally, a little more triangular in lateral view and narrower in dorsal view.

Remarks. Xestoleberis subtriangularis sp. nov. differs from all other species herein studied mainly in the subtriangular shape in lateral view and the conspicuous eye-spot. This species is similar to X. ferax Klie, 1940 described from South-West Africa ( Namibia), differing in the posterior end, which is more rounded in the African species. Also, the carapace of X. subtriangularis sp. nov. is more tumid and the Xestoleberis -spot is longer and not outlined.

Occurrence and distribution. Xestoleberis subtriangularis sp. nov. occurs along the Northeastern and Eastern regions of the Brazilian continental shelf ( Fig. 2 ; Tab. 1), between 16 and 92 m of depth.

Figures

FIGURE 2. Distribution of Xestoleberis species in Brazilian continental shelf. The hatched area corresponds to the Transitional Zone of Coimbra et al. (1995). Each dot represents one sample.

FIGURE 5. Xestoleberis subtriangularis sp. nov. 1. Female, RV (MP-O- 1692, holotype). 2. Female, LV (MP-O- 1694). 3. Female, dorsal view (MP-O- 1695). 4. Male, RV (MP-O- 1693). 5. Male, LV (MP-O- 1693). 6. Central muscle scars, RV (MP-O- 1696). 7. Hinge (MP-O- 1697). 8. Sieve-type normal pore canal (MP-O- 1692, holotype). 9. Lip-type normal pore canal (MP-O- 1692, holotype). 10. Xestoleberis - spot (MP-O- 1697). 11. Schematic drawing of some LV internal features.