Issacharella bisulcata Kozur, 1972

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 : 394-395

Issacharella bisulcata Kozur, 1972

emend. Kristan-Tollmann in Kristan-Tollmann et al. (1991b) ( Fig. 8 I-U)

Issacharella bisulcata Kozur, 1972: 22, pl. 1, figs 1, 5-7 — Kristan- Tollmann et al. 1991b: 205, pl. 3, fig. 2; pl. 4, figs 1-3, 5-7.

EXAMINED MATERIAL. — More than 100 specimens, including isolated valves and complete carapaces.

OCCURRENCE. — Carnian, Late Triassic, Veszprem, Balatón highland, Hungary (Kozur 1972); Carnian, Late Triassic,Transdanubian range, Hungary (Kristan-Tollmann et al. 1991b); Nicoraella ? budaensis conodont zone, late Julian-?earliest Tuvalian, Carnian, Late Triassic, samples BE2, 17, 18, 21, 23/1 ( Fig. 3 ), Belca section, ‘Raibl Beds’, Karavanke Mountains, Slovenia (this work).

DIMENSIONS. — Fig. 10.

DISCUSSION

Issacharella bisulcata Kozur, 1972 emend. Kristan-Tollmann in Kristan-Tollmann et al. (1991b) has been found in all samples of the Belca section, where it is relatively abundant except for sample BE23/1 ( Fig.3 ). Until the present record, this species was only recorded from the Carnian of Hungary.Kristan-Tollmann et al. (1991b) considered that this species was described on early juveniles and that the holotype designated by Kozur (1972) was a late juvenile. The largest known specimen is recorded from Belca section and confirms the diagnostic of Kristan-Tollmann et al. (1991b) that the holotype of I. bisulcata is not an adult. The only four carapaces of this species, all from the Belca section, show that the overlap is present quite early in the development of this species ( Fig. 10 ). As was already identified by Kristan- Tollmann et al. (1991b), the ontogeny of I. bisulcata is mainly marked by the enlargement of the posterior margin, which is narrow in young specimens and becomes larger during the ontogeny. The carapaces of young juveniles are therefore more assymetric in lateral view (e.g., Fig. 8 I-K) than older juveniles and adults (e.g., Fig. 8 R-U), with slightly less convex ventral margin and a straight to only slightly convex dorsal margin.

Figures

FIG. 8. — 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-E, Renngartenella sanctaecrucis Kristan-Tollmann in Kristan-Tollmann & Hamedani, 1973; A, lateral view of a right valve, BE2 (GeoZS6195); B, lateral view of a left valve, BE2 (GeoZS6196); C, lateral view of a right valve, BE2 (GeoZS6197); D, lateral view of a left valve, BE2 (GeoZS6198); E, lateral view of a right valve, BE2 (GeoZS6199); F, Hungarella sp. 1, lateral view of a right valve, BE18 (GeoZS6200); G, Hungarella sp. 2, lateral view of a right valve, BE18 (GeoZS6201); H, Cardobairdia? sp., right lateral view of a complete carapace, BE17 (GeoZS6202); I-U, Issacharella bisulcata Kozur, 1972 emend. Kristan-Tollmann in Kristan-Tollmann et al. 1991b; I, lateral view of a right valve, BE18 (GeoZS6203); J, lateral view of a left valve, A-5, BE21 (GeoZS6204); K, lateral view of a right valve, A-4, BE2 (GeoZS6205); L, lateral view of a left valve,A-4,BE2 (GeoZS6206);M, lateral view of a right valve,BE2 (GeoZS6207);N, lateral view of a right valve,BE18 (GeoZS6208);O, lateral view of a left valve,A-3, BE2 (GeoZS6209); P, left lateral view of a carapace,A-2, BE17 (GeoZS6210); Q, lateral view of a right valve, BE21 (GeoZS6211); R, lateral view of a left valve, A-1, BE17 (GeoZS6212); S, lateral view of a right valve, A-1, BE2 (GeoZS6213); T, left lateral view of a carapace, Adult, BE17 (GeoZS6214); U, lateral view of a left valve, Adult, BE18 (GeoZS6215). Scale bars: 100 μm.

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

FIG. 10. — Height/Length scatter plots of Issacharella bisulcata Kozur, 1972 emend. Kristan-Tollmann in Kristan-Tollmann et al. (1991b). The dimensions of right and left valves of complete carapaces are linked.