Acratia cf. Acratia sp. A in Bolz 1971

Fig. 5A

Material examined

ROMANIA • 1 complete carapace; Black Sea, Romanian Continental Shelf, borehole 817LV, sample CM31B; Rhaetian, Upper Triassic; MNHN.F. F63181 • 1 LV; same locality as for preceding but sample CM31C; Rhaetian, Upper Triassic; MNHN.F. F63341 .

Dimensions

Bolz (1971b) provided measurements for two carapaces and a RV. Here we equate the measurements of carapaces with those of the larger LV to allow for comparisons (Table 3).

Occurrence

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

Remarks

This species differs from Acratia sp. A in Bolz 1971b from the Norian–Rhaetian of the Northern Calcareous Alps (Bolz 1971b) in being slightly more elongate, having a more pronounced ventral concavity, a more angulate dorsal margin at LV and a rostrum located higher. The two species are nevertheless close morphologically as shown by the antero-dorsal offset of LV over RV. The complete carapace recovered here is slightly smaller than the specimens reported from Austria (Table 3) and could represent an immature juvenile. We cannot exclude that the observed differences relate to ontogeny, the antero-dorsal offset being a diagnostic character of the species. Acratia cf. Acratia sp. A in Bolz 1971 is also close to A. goemoeryi Kozur, 1970 from the Middle Triassic of Hungary (Kozur 1970). Forel et al. (2019a) plotted the H/L diagram of all known specimens of A. goemoeryi, in which the present specimen could correspond to a relatively young juvenile stage. Several isolated valves or poorly preserved carapaces of A. goemoeryi have been documented from the Middle Triassic and early Late Triassic, which do not allow for the observation of the possible dorsal offset visible in Acratia sp. A in Bolz 1971 and Acratia cf. Acratia sp. A in Bolz 1971. Furthermore, the ADB of RV is arched in A. goemoeryi while it is concave in the present material.