Sphaerulites boreaui Toucas, 1908

Săsăran, Liana, Săsăran, Emanoil & Bucur, Ioan I., 2018, Upper Cretaceous Rudist-Bearing Mixed Siliciclastic-Carbonate And - Volcanoclastic Deposits From Strâmturii Valley, Borod Basin, Northern Apuseni Mountains: Description, Microfacies And Depositional Environments, Acta Palaeontologica Romaniae 14 (1), pp. 3-20 : 12-14

Sphaerulites boreaui Toucas, 1908

Fig. 7 j-k.

1908 Sphaerulites boreaui nov. sp. - Toucas, p. 56, pl.9, fig.6, text-figs. 28-29.

1976 Sphaerulites boreaui Toucas- Lupu, p. 129, pl.20, fig.1a-b.

2000 Sphaerulites cf. boreaui Toucas- Pleničar and Jurkovsek, p. 59, pl.3, fig.1.

Material: 1 specimen, both valves (BBU-MPS-24084).

Description: The shape of right valve is conical, rapidly expanding, having 40 mm height and 110 mm diameter antero-posterior. Growth lamellae of RV are subhorizontal, markedly expanded. In postero-ventral area, radial structures are not visible because the valves are broken. Left valve is slightly convex, thin and smaller than RV, measuring 15 mm heigh and 60 mm the antero-posterior diameter ( Fig. 7j ). In transverse section through the valves near the commissure, the ligament ridge is visible having a long pedicle, 16 mm length, and expand- ed distal end ( Fig. 7k ); two dorsal cavities developed between the ligament ridge and the myocardinal apparatus ( Fig. 7k ). The cellular outer shell layer of RV has variable thickness; largest toward the anterior side, with cells extremely radially elongated giving the appearance of radial ridges ( Fig. 7k ).

outer shell layer, positions of radial bands (Vb and Pb), the length of ligamental ridge and myocardinal apparatus. Remarks: Our specimen is similar with species of Sphaerulites boreaui previously described by Lupu (1976) from Late Santonian deposits from RoȘia Basin.

Age and distribution: early-middle Santonian in France ( Toucas, 1907), late Santonian-early Campanian in Bosnia-Herzegovina ( Sliskovic, 1971), Slovenia ( Pleničar and Jurkovsek, 2000), Romania ( Lupu, 1976) and Spain ( Vicens, 1992).

Figures

Fig. 7 a, b Bournonia excavata d'Orbigny, 1847, (inventory no. 24078 BBU-MPS =no.1246 sample field); a transverse section through RV close to the commissure, showing the myocardinal elements: anterior and posterior tooth and myophores (am, pm) of the opposite valve; b view of flat posteroventral side of RV; c Gorjanovicia endrissi (Böhm)(24079 BBU-MPS) – transverse section of RV showing compact layer, concave ventral band (Vb); Ib- narrow and wide Pb with 3 fine rounded costae; d, e Praeradiolites subtoucasi (Toucas): d transverse section through RV (24080-BBU-MPS), unknown commissure. The outer shell layer from ventral side is eroded thus the radial bands are missing. e transverse section on other specimen (24081-BBU- MPS) having outer shell layer partially broken but preserve the myocardinal apparatus. f, g Radiolites squamosus (d'Orbigny): f specimen with both valves showing convex LV, very eroded and the ornamentations of RV consist in dense growth lamellae (sample no. 24082 BBU-MPS); g ventral side of RV of the same specimen showing radial bands (Vb and Pb) with folds upward to commissure and the narrow interband (Ib). h-i Radiolites nouleti (Bayle)(sample no. 24083 BBU-MPS): h large conical RV, thick-shelled, with dense folded growth lamellae, slightly ondulated in large interband (Ib); i transverse section in RVof the same specimen, showing thick cellular outer shell layer, ligamental ridge and accessory cavities. j, k Sphaerulites boreaui (Toucas)(sample no. 24084 BBU-MPS), j specimen with both valves, top view, showing LV, thin and smaller than lower valve and large RV with expanded, sub-horizontal growth lamellae; k transverse section through RV, showing thickness of cellular