| Measurements | D mm | H/D | T/D | O/D | H/T |
|---|---|---|---|---|---|
| BM C11477 Spath 1923 | 57 | 0.51 | 0.26 | 0.16 | 1.96 |
| CP-549 | 57 | 0.53 | 0.27 | 0.16 | 1.94 |
| CP-70 | 85.2 | 0.51 | 0.26 | 0.17 | 1.95 |
| RJ-96 figured | 268 | 0.42 | 0.20 | 0.21 | 2.09 |
| Age | Origin |
|---|---|
|
Phosphatic Bed P5 Saint-Pô Formation (grey clay) D. cristatum zone, Upper Albian |
Wissant Pas-de-Calais France |
Description. Ammonite in black phosphate, with portions of suture lines and test remnants in the form of a coppery film. The shell is compressed and highly involute. The whorl section is very high, with slightly convex flanks converging towards a narrowly arched venter. The small umbilicus with a smooth subvertical wall is connected to the flank by an angular edge. The suture lines are very finely incised and tangent, meaning that two successive septa touch at several points. The flanks are smooth, except for minute undulations along the spiral, visible only in raking light and effaced on the venter.
Remarks. The image on the right shows the deep divisions of the first lateral lobe on CP-70 (the front is at the top). The species resembles three other compressed Beudanticeras: B. laevigatum and B. newtoni from the Anglo-Paris Basin, and B. revoili from the Tethyan Zone (see their entries). However, they have a less complex suture and are restricted to the Lower Albian (plus the lyelli subzone of the benettianus zone, at the base of the Middle Albian, in the case of B. laevigatum), while B. beudanti covers the first two zones of the Upper Albian (cristatum and pricei). This is why Latil et al. (2023) propose to retain the upper Albian forms such as B. beudanti and B. haydeni (Gabb, 1864) in the genus Beudanticeras, and to assign the other species to a new genus, Roberticeras.