Bairdia sp. 7, 1844

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 : 16-18

Bairdia sp. 7 in Mette & Mohtat-Aghai 1999

Fig. 5 D–G

Bairdia sp. 7 – Mette & Mohtat-Aghai 1999: pl. 4, figs 4–5.

Material examined

ROMANIA • 1 RV; Black Sea , Romanian Continental Shelf , borehole 817LV, sample CM31B; Rhaetian, Upper Triassic; MNHN.F. F63184 • 1 RV; same locality as for preceding but sample CM31A; Rhaetian, Upper Triassic ; MNHN.F. F63185 • 1 LV; same locality as for preceding but sample CM31B; Rhaetian, Upper Triassic; MNHN.F. F63186 • 2 complete carapaces, 5 RV, 4 LV; same locality as for preceding but samples CM31A, CM31B and CM31C; Rhaetian, Upper Triassic; MNHN.F. F63342 .

Dimensions (this paper)

RV: L = 372–1138 µm; H = 200–603 µm; H/L = 0.53–0.56.

LV: L = 372–1212 µm; H = 205–768 µm; H/L = 0.55–0.63.

Occurrence

Kössen Formation, Northern Calcareous Alps, Tyrol, Austria, Rhaetian, Upper Triassic (Mette & MohtatAghai 1999); Romanian Continental Shelf, Black Sea, Rhaetian, Upper Triassic (this paper).

Remarks

Bairdia sp. 7 in Mette & Mohtat-Aghai 1999 was first recorded from the Kössen Formation outcropping in the Northern Calcareous Alps ( Mette & Mohtat-Aghai 1999). This species is higher and slightly shorter than B. cassiana ( Reuss, 1869) , which is largely documented from the Early Anisian–Late Carnian interval of Europe ( Reuss 1869; Gümbel 1869; Styk 1958; Urlichs 1972; Kristan-Tollmann 1978; Kristan-Tollmann et al. 1991b; Monostori 1995; Crasquin-Soleau & Grădinaru 1996; Monostori & Tóth 2013, 2014; Mette et al. 2015; Crasquin et al. 2018; Forel et al. 2020). It also shares morphological proximity with B. jiangyouensis Xie in Wei et al., 1983 from the Carnian–Norian interval of Sichuan Province, South China ( Wei et al. 1983; Forel et al. 2019b), from which it differs by a larger and slightly less caudate posterior end and an anterior maximum of convexity located lower. Bairdia jiangyouensis is also characterized by having LV overlapping RV all around: the nature of the overlap cannot be completely characterized for the present species as only juvenile carapaces have been found, with an interrupted overlap along AVB and AB. Bairdia sp. 7 in Mette & Mohtat-Aghai 1999 also differs from Bairdia sp. A in Bolz 1971 from the Zlambach Formation, Norian–Rhaetian, of the Northern Calcareous Alps ( Bolz 1971a: pl. 7, figs 82–83) in having a tripartite dorsal margin on RV, while it is uniformly convex in Bairdia sp. A. It also differs from Bairdia sp. B in Bolz 1971 ( Bolz 1971a: pl. 7, figs 82–83) by having its DB inclined posteriorly, PB larger and less caudate and AVB less convex and anteriorly projected. It is also close to Bairdia sp. in Kristan-Tollmann 1979 from the Rhaetian of Iran ( Kristan-Tollmann et al. 1979), but the RV of the Iranian species has a shorter posterior end, a pronounced concavity at the ADB and a slight concavity at the base of the AVB. Crasquin et al. (2018) recently considered that Bairdia sp. 3 from the Carnian, Late Triassic, of Sicily ( Crasquin et al. 2018: fig. 6u) might be conspecific with Bairdia sp. 7 in Mette & Mohtat-Aghai 1999. However, the specimen shown in Crasquin et al. (2018) has a longer and more caudate posterior border, with AVB and PVB slightly compressed laterally in their median extremity. For this reason, we do not consider these taxa to be conspecific. Bairdia sp. 7 in Mette & Mohtat-Aghai 1999 is undeniably new to science, but it is kept in open nomenclature until complete carapaces are discovered to fully describe the overlap of the LV over RV. The description of the ontogeny of the species listed above will allow the clarification of their possible conspecificities, but until now most of them are only know from a few specimens.

Figures

Fig. 5 (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. Acratia cf. Acratia sp. A in Bolz 1971, right lateral view of a carapace, sample CM31B (MNHN.F.F63181). B. Acratia sp. 1, external view of a right valve, sample CM31C (MNHN.F.F63182). C. Acratia sp. 2, right lateral view of a carapace, sample CM31A (MNHN.F.F63183). D–G. Bairdia sp. 7 in Mette & Mohtat-Aghai 1999. D. External view of a right valve, sample CM31B (MNHN.F.F63184). E. External view of a right valve, sample CM31A (MNHN.F.F63185). F. External view of a left valve, sample CM31B (MNHN.F.F63186). G. Same specimen, inner view. H–I. Bairdia cf. parva Ainsworth, 1987. H. Right lateral view of a carapace, sample CM31B (MNHN.F.F63187). I. Right lateral view of a carapace, sample CM31B (MNHN.F.F63188). J–K. Bairdia sp. 3. J. Right lateral view of a carapace, sample CM31A (MNHN.F.F63189). K. Right lateral view of a carapace, sample CM31C (MNHN.F.F63190). L–N. Bairdia sp. 4. L. Right lateral view of a carapace, sample CM31C (MNHN.F.F63191). M. Right lateral view of a carapace, sample CM31B (MNHN.F.F63192). N. Same specimen, dorsal view. O–Q. Bairdia sp. 5. O. Right lateral view of a carapace, sample CM31C (MNHN.F.F63193). P. Same specimen, dorsal view. Q. Right lateral view of a carapace, sample CM31B (MNHN.F.F63194). R. Bairdia sp. 6, external view of a left valve, sample CM31C (MNHN.F.F63195). S–T. Bairdia sp. 7. S. Right lateral view of a carapace, sample CM31B (MNHN.F.F63196). T. Same specimen, dorsal view. U. Bairdia sp. 8, right lateral view of a carapace, sample CM31B (MNHN.F.F63197). Scale bars: 100 µm.