| 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 | 268 | 0.42 | 0.20 | 0.21 | 2.09 |
| Age | Origin |
|---|---|
|
Grey limestone bed Top of Argiles tégulines formation M. pricei zone, Upper Albian |
L'Étape Mathaux, Aube France |
Description. A very large discoid ammonite, on a block of gray limestone used as a base. The aperture is not cleared. The shell is replaced by a dark brown patina that reveals deeply incised sutures. The body chamber, which occupies the last half-whorl, has almost stopped increasing in height. The spire is very involute. The lanceolate cross-section is very high, with nearly flat flanks that diverge up to 40% of their height, then converge towards a very narrow but not acute venter. The small umbilicus opens towards the end, with a smooth, almost vertical wall sloping at 80° and an angular edge. The flanks are smooth, but in raking light, growth lines are visible on the diverging portion of the flanks, as well as six faint undulations on the outer half of the last whorl. No constrictions are observed.
Remarks. Specimen found during the construction of the Lac du Temple (aka Réservoir Aube) discharge canal at a place called L'Étape, in the commune of Mathaux, and already illustrated in Jaffré et al. (2022, p. 95). To my knowledge, no specimen of this size is illustrated in the literature or preserved in a museum.