Isobythocypris sp, Apostolescu, 1959

Forel, Marie-Béatrice & Grădinaru, Eugen, 2020, Rhaetian (Late Triassic) ostracods (Crustacea, Ostracoda) from the offshore prolongation of the North Dobrogean Orogen into the Romanian Black Sea shelf, European Journal of Taxonomy 727, pp. 1-83 : 38

Isobythocypris sp .

Fig. 9A

Material examined

ROMANIA • 1 complete carapace; Black Sea , Romanian Continental Shelf , borehole 817LV, sample CM31C; Rhaetian, Upper Triassic; MNHN.F. F63245 • 1 complete carapace; same collection data as for preceding; Rhaetian, Upper Triassic; MNHN.F. F63353 .

Dimensions

RV: L = 470–780 µm; H = 268–427 µm; H/L = 0.55–0.57.

LV: L = 480–798 µm; H = 275–466 µm; H/L = 0.58.

Occurrence

Romanian Continental Shelf, Black Sea, Rhaetian, Upper Triassic (this paper).

Remarks

Isobythocypris Apostolescu, 1959 is mainly distinguished from other bairdiid genera by its lophodont hinge ( Apostolescu 1959). More recently, Ainsworth (1990) clarified that Isobythocypris has a subrectangular to elongate subrectangular lateral outline. Only complete carapaces have been retrieved from the CM31 sample so it is impossible to characterize the nature of the hinge in the present material. However, because of its sub-rectangular outline it is attributed to Isobythocypris . Isobythocypris sp. resembles I. dorsoconvexa Ainsworth, 1987 and I. pliensbachensis Ainsworth, 1987 both from the Pliensbachian, Early Jurassic, of the Fastnet Basin, offshore Southwest Ireland ( Ainsworth 1987), from which it differs by its shorter oral concavity, less pronounced lateral compression along AVB and its visible, although poorly expressed, dorsal angulations. Isobythocypris sp. is also close to Bairdiacypris triassica postera Herrig, 1979 from the Upper Sinemurian, Early Jurassic, of Thüringen, Germany ( Herrig 1979b), but it differs in being more massive and less elongate, with a longer posterior end and a more tapered anterior end.

Figures

Fig. 9 (opposite page). SEM micrographs of ostracods from borehole 817 Lebăda Vest, drill core CM31, western portion of Black Sea shelf, Rhaetian, Late Triassic. All specimens are housed in the collections of the Muséum national d’histoire naturelle, Paris, France (MNHN). A. Isobythocypris sp., right lateral view of a carapace, sample CM31C (MNHN.F.F63245). B–I. Isobythocypris atalantella Forel sp. nov. B. Holotype, right lateral view of a carapace, sample CM31B (MNHN.F.F63246). C. Same specimen, ventral view. D. Paratype, right lateral view of a carapace, sample CM31B (MNHN.F.F63247). E. Right lateral view of a carapace, sample CM31B (MNHN.F.F63248). F. Right lateral view of a carapace, sample CM31B (MNHN.F.F63249). G. Right lateral view of a carapace, sample CM31C (MNHN.F.F63250). H. Right lateral view of a carapace, sample CM31B (MNHN.F.F63251). I. Same specimen, dorsal view. J–M. Lobobairdia salinara Kollmann, 1963. J. External view of a right valve, sample CM31B (MNHN.F.F63252).K. External view of a left valve, sample CM31B (MNHN.F.F63253). L. External view of a left valve, sample CM31B (MNHN.F.F63254). M. External view of a left valve, sample CM31C (MNHN.F.F63255). N. Lobobairdia? sp. 1, right lateral view of a carapace, sample CM31B (MNHN.F.F63256). O. Lobobairdia sp. 2, right lateral view of a carapace, sample CM31C (MNHN.F.F63257). P. Mirabairdia sp., external view of a left valve, sample CM31A (MNHN.F.F63258). Q–U. Petasobairdia amazonella Forel sp. nov. Q. Right lateral view of a carapace, sample CM31C (MNHN.F.F63259). R. Right lateral view of a carapace, sample CM31A (MNHN.F.F63260).S. Paratype, right lateral view of a carapace, sample CM31B (MNHN.F.F63261). T. Same specimen, dorsal view. U. Right lateral view of a carapace, sample CM31B (MNHN.F.F63262). Scale bars: 100 µm.