| Species | Coroniceras tardesulcatus (WÄHNER) |
| Author | WÄHNER |
| Group | Arieten |
| Horizon | rotiformis-horizon |
| Zone | rotiformis-zone |
| Stage | Lower Sinemur |
Description
The cross-section of the windings is round, the housing is involute. The flanks are convex. The ribs run radially across the flank at regular intervals and bend forward near the external side, where they then extinguish. There is nu purely faint node to be observed, on smaller specimens it may still be absent.
Such small specimens do not yet have a keel. It only starts to appear as a faint elevation from a diameter of approx. 10mm. With increasing development it becomes stronger with shallow furrows.
Description according to Waehner (1894)
Compare
C. tardesulcatus differs from C. rotiforme in the shallow and late keel formation. The coils are less thick and the ribs weaker.
The most similar is C. insulcatus, which shows no keel even in larger specimens. Nevertheless, it is not excluded that they are extreme forms of the very variable species C. rotiformis.
Dimension
Dimensions with D= 77mm
Nw % v. D: 56%
Wh % v. D: 25%
Wb % v. D: 27%
Literature
1894 Arietites rotiformis Sow.var. tardesulcatus n.f..– Wähner, S. 210, Taf 51.7-8, 52.1-2
