Bairdia balatonica Méhes, 1911

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 : 382-384

Bairdia balatonica Méhes, 1911

( Fig. 4E )

Bairdia balatonica Méhes, 1911: 13 , 14, pl. 1, fig. 8-11. — non Széles 1965: 414, fig. 4. — Monostori 1995: 42, pl. 2, fig. 1 only. —? Monostori 1995: 42, pl. 2, figs 2, 3. — Forel & Crasquin 2011: 252, fig. 5A. — Monostori & Tóth 2013: 309, pl. 2, figs 1-4 only. —? Monostori & Tóth 2013: 309, pl. 2, fig. 5. — Crasquin et al. 2018: 134, 135, fig. 6P.

Bairdia cf. balatonica – Méhes in Kristan-Tollmann 1978: 81, pl. 1, figs 1-3.

Bairdia dadayi Méhes, 1911: 17 , 18, pl. 1, figs 29, 30. — Széles 1965: 412, 413, fig. 1.

EXAMINED MATERIAL. — One left valve and several fragments.

OCCURRENCE. — Spathian-Anisian, Early-Middle Triassic, South Tibet (Forel & Crasquin 2011) ; Anisian ( Monostori 1995), La- view of a right valve, BE18 (GeoZS6145); O -U, Dicerobairdia buseri Forel , n. sp.; O, Holotype,lateral view of a left valve, BE18 (GeoZS6146); P, right lateral view of a complete carapace, BE21 (GeoZS6147); Q, lateral view of a left valve, BE17 (GeoZS6148); R, lateral view of a left valve, BE18 (GeoZS6149); S, Paratype, lateral view of a right valve, BE18 (GeoZS6150); T, lateral view of a right valve, BE18 (GeoZS6151); U, lateral view of a left valve,BE18 (GeoZS6152). Scale bars: 100 μm. dinian ( Monostori & Tóth 2013) and early Carnian ( Méhes 1911; Széles 1965), Middle-Late Triassic, Balatón Highland, Hungary ; early Carnian, Late Triassic, Southern Alps, Italy (Kristan-Tollmann 1978); 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. 5A.

DISCUSSION

This species occurs in samples BE17, 18, 21 and 23/1 of the Belca section but it is not abundant ( Fig. 3 ). Bairdia balatonica Méhes, 1911 was described from the early Carnian, Late Triassic, of Hungary ( Méhes 1911). Since then, it has been more largely documented and appears as typical of the Spathian-Carnian time interval, spreading from South Tibet (Forel & Crasquin 2011) to Hungary (e.g., Monostori 1995; Monostori & Tóth 2013). Bairdia balatonica identified from the early Carnian, Late Triassic, of Hungary by Széles (1965) is excluded because the drawn specimen is very asymmetric laterally and the right valve is uniformly rounded without the anterodorsal and posterodorsal angulations shown on the type material of Méhes (1911). Of the three specimens attributed to B. balatonica Méhes, 1911 in Monostori (1995) from the Anisian, Middle Triassic, of Hungary, two have a triangular dorsal overlap ( Monostori 1995: pl. 2, figs 2, 3): the attribution to B. balatonica is therefore questioned. One of the five specimens from the Ladinian, Middle Triassic, of Hungary ( Monostori & Tóth 2013) is questioned as belonging to B. balatonica for the same reason ( Monostori & Tóth 2013: pl. 2, fig. 5). These three specimens from the Middle Triassic of Hungary ( Monostori 1995; Monostori & Tóth 2013) might represent an undescribed species characterized by its triangular dorsal overlap of left valve over right one. Lastly, Monostori & Tóth (2013) considered that B. ventriosa Bolz, 1971 from the late Norian-Rhaetian, Late Triassic, of the Northern Calcareous Alps (Bolz 1971) fit into the variations of the lateral outline of B. balatonica . However, the surface of B. ventriosa is evenly pitted so that we do not consider this synonymy as relevant.

The dimensions of all Carnian specimens available in the literature that are considered as truly belonging to B. balatonica have been plotted in Fig. 5A . The Carnian specimens gather into four scatter plots, which might correspond to the ontogenetic stages A-3 to Adult. However, each of the identified group correspond to one specimen from one locality: for this reason and until more material is made available, we choose not to attribute precise ontogenetic stages to these groups. For the Carnian stage, the largest specimens are reported from Italy (Kristan-Tollmann 1978). The development of B. balatonica is marked by the elongation of the valves, from plump and short posteriorly for the smaller specimen shown in Crasquin et al. (2018), to more elongate with dorsal angulations, slightly caudate posterior border and more pronounced posterodorsal concavity in the largest materiel illustrated byKristan-Tollmann (1978).

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.