Bairdia cassiana ( Reuss, 1869 )

Forel, Marie-Béatrice, Kolar-Jurkovšek, Tea & Jurkovšek, Bogdan, 2020, Ostracods from the ‘ Raibl Beds’ (Carnian, Late Triassic) of Belca section in Karavanke Mountains, northwestern Slovenia, Geodiversitas 42 (21), pp. 377-407 : 384

Bairdia cassiana ( Reuss, 1869)

( Fig. 4 F-H)

Cythere cassiana Reuss, 1869: 108 .

Bairdia cassiana – Gümbel 1869: 180, pl. 5, figs 18, 19. — Styk 1958: 171, fig. 3/1. — Urlichs 1970: 705, 706, pl. 1, figs 1, 2. — Kristan-Tollmann 1978: 81, pl. 1, fig. 4; pl. 6, fig. 6. — Kristan-Tollmann et al. 1991b: 200, pl. 1, fig. 5. — Monostori & Tóth 2013: 310, pl. 2, figs 7, 8, 10; 2014: 26, pl. 1, fig. 14. — Mette et al. 2014: pl. 2, fig. 1. — Crasquin et al. 2018: 134, fig. 6M.

Bairdia cassiana rotundidorsata Monostori, 1995: 42 , pl. 2, figs 4, 5. Bairdia (Rectobairdia) garciai Crasquin-Soleau & Grădinaru, 1996: 77 , 78, pl. 2, figs 5, 8.

EXAMINED MATERIAL. — Four right valves, four left valves and several fragments.

OCCURRENCE. — Early Carnian, Late Triassic, Southern Alps, Italy ( Reuss 1869; Gümbel 1869; Urlichs 1970; Kristan-Tollmann 1978); Carnian, Late Triassic, Święty Krzyż Mountain, Poland ( Styk 1958); Carnian, Late Triassic, Zsämbek-14 borehole,Transdanubian Range, Hungary (Kristan-Tollmann et al. 1991b); Late Anisian, Middle Triassic, Balatón Highland, Hungary ( Monostori 1995); Early Anisian, Middle Triassic, North Dobrogea, Romania (Crasquin-Soleau & Grădinaru 1996); Ladinian, MiddleTriassic, Balatón Highland, Hungary ( Monostori & Tóth 2013, 2014); Middle Anisian, Middle Triassic, Northern Calcareous Alps, Austria ( Mette et al. 2014); Tropites dilleri zone, late Carnian, Late Triassic, Sicily, Italy (Crasquin et al. 2018); Nicoraella ? budaensis conodont zone, late Julian-?earliest Tuvalian, Carnian, Late Triassic, samples BE17, 18, 21, 23/1 ( Fig. 3 ), Belca section, ‘Raibl Beds’, Karavanke Mountains, Slovenia (this work).

DIMENSIONS. — Fig. 5B.

DISCUSSION

Bairdia cassiana ( Reuss, 1869) has been found in all samples from BE17 to BE23/1 where it is not abundant, and it is moderately abundant in BE18 ( Fig. 3 ). Bairdia cassiana is typical of the Middle and early Late Triassic of Europe, as shown by the synonym list. The height/length scatter plot of all Carnian specimens is shown in Fig. 5B (the dimensions of the specimens cited without mention of their nature, i.e. right valve, left valve or carapace, have been omitted). The largest specimens are from the Ladinian of Hungary ( Monostori & Tóth 2013, 2014). The separate measurements of right and left valves of complete carapaces show that the degree of overlap is relatively constant during the ontogeny of this species. The left valve is slightly longer than the right valve in the first instars compared to later stages. The ontogenetic development of B. cassiana is also marked by the elongation of the posterior border.

Figures

FIG. 4. — Ostracods from the Belca section, Karavanke Mountains, northwestern Slovenia, Carnian, Late Triassic. All specimens are deposited in the micropalaeontology collections of the Geological Survey of Slovenia, under the numbers GeoZS6132 to GeoZS6239, preceded by sample number: A, B, Acratia cf. goemeryi Kozur, 1970 emend. Forel et al. (2019a); A, lateral view of a right valve, BE21 (GeoZS6132); B, lateral view of a left valve, BE18 (GeoZS6133); C, Acratia sp. 1, lateral view of a broken left valve, BE18 (GeoZS6134); D, Acratia sp. 2, lateral view of a left valve, BE18 (GeoZS6135); E, Bairdia balatonica Méhes, 1911, lateral view of a left valve, BE17 (GeoZS6136); F-H, Bairdia cassiana (Reuss, 1869); F, lateral view of a right valve, BE18 (GeoZS6137); G, lateral view of a right valve, BE18 (GeoZS6138); H, right lateral view of a complete carapace, BE23/1 (GeoZS6139); I, Bairdia cf. perpusilla sensu Forel et al. (2019a), lateral view of a left valve, BE17 (GeoZS6140); J, Bairdia sp. 1, right lateral view of a complete carapace, BE18 (GeoZS6141); K, Bairdia sp. 2, lateral view of a right valve, BE23/1 (GeoZS6142); L, M, Bairdia sp. 3; L, lateral view of a left valve, BE18 (GeoZS6143);M, lateral view of a left valve, BE18 (GeoZS6144); N, Bairdiacypris sp. 1, lateral

FIG. 3. — Distribution of ostracod species through the Belca section, Karavanke Mountains, northwestern Slovenia.

FIG. 5. — Height/Length scatter plots of species recovered from the Belca section, Karavanke Mountains, northwestern Slovenia, Carnian, Late Triassic. In all diagrams, the dimensions of right and left valves of complete carapaces are linked. A, Bairdia balatonica Méhes, 1911; B, Bairdia cassiana (Reuss, 1869); C, Dicerobairdia buseri Forel, n. sp., all specimens are from the Belca section (this work); D, Mirabairdia longispinosa Kristan-Tollmann, 1978; E, Pontocypris? karavankensis Forel, n. sp. all specimens are from the Belca section (this work). Scale bars: 100 μm.