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.