| Species | Angulaticeras ventricosum (SOWERBY) |
| Author | SOWERBY |
| Group | Schlotheimien |
| Horizon | rotiformis-horizon |
| Zone | rotiformis-zone |
| Stage | Lower Sinemur |
Description
The turn cross-section is highly oval with slightly curved, flattened flanks. The external side is more and more sharpened with increasing development. The umbilical drop is broadly rounded.
The ribs are thin and quite numerous. They start at the seam and run slightly s-shaped, but still largely straight across the flanks and meet externally at a 180° angle, leaving a narrow furrow free. Near the external side they bend only slightly forward. Even in large specimens, the weakening of the ribbing is hardly noticeable.
Wähner lists two variants: thinner shells with finer ribs and thicker ones with stronger ribs.
This species can be clearly identified if it is found in a calcareous bank above the marmoreum crust, where no similar Angulaticeras (A. marmoreum, A. trapezoidale) occur any more.
Wähner also always describes the species from the younger horizon together with Coroniceras rotiforme from Enzesfeld.
* Description according to Wähner (1884), supplemented
Compare
Compared to Angulaticeras marmoreum, this species is clearly more narrowly forked and the ribs appear straighter on the flanks.
Angulaticeras trapezoidale has much stronger ribs and a larger Wb with evenly curved flanks.
Dimension
Dimensions with D=110mm
Nw % v. D: 23 %
Wh % v. D: 47 %
Wb % v. D: 23 %
Literature
- 1884 Aegoceras ventricosum Sow. (Can.) – Wähner S. 186, Taf. 23.15-18, Taf. 26.1-2
