| Measurements | D mm | H/D | T/D | O/D | H/T |
|---|---|---|---|---|---|
| Holotype | 27 | 0.45 | 0.26 | 0.22 | 1.73 |
| Spath pl.24 fig.12 | 29 | 0.45 | 0.29 | 0.23 | 1.55 |
| CP-676 | 34.3 | 0.44 | ? | 0.22 | ? |
| Spath pl.24 fig. 1 | 45 | 0.41 | 0.26 | 0.30 | 1.58 |
| CP-675 | 63.2 | 0.44 | 0.25 | 0.26 | 1.73 |
| Age | Origin |
|---|---|
|
Gaize of Argonne M. perinflatum zone Terminal Albian (Vraconnian) |
Passavant-en-Argonne Marne, France |
Description. A slightly deformed, sutureless, discoid internal mold, preserved in a block of gaize and coated with a limonitic film. The whorls, 60% covered, have a compressed trapezoidal section, with barely convex flanks converging slightly towards a discreetly fastigiate venter. Indeed, the venter is rounded but somewhat flattened, with an obtuse fold along the siphonal line. The umbilicus has a subvertical wall and an angular edge. The weak ribs were made visible by oblique lighting. On the penultimate half-whorl, there are 12 small, tightly packed, proverse bullae on the umbilical edge, from which proverse, falciform ribs arise in pairs or groups of three (28), terminating in small ventrolateral clavi almost parallel to the siphon. A few pairs of ribs are lautiform. The ribs and their tubercles gradually fade and become more spaced on the last half-whorl, where they are only visible in raking light. The photo on the right illustrates specimen CP-676, which is smaller and comes from the same deposit.
Remarks. CP-675 and 676 (personal discoveries) closely resemble the specimens in pl. 24 fig. 1 and 12 of Spath (1926) and pl. 5 fig. 9 of Amédro (2002). The falcate ribs, according to Spath, do not have the straight lower portion of some Cleoniceras. They are proverse, slightly convex up to mid-flank, then concave and more curved, and finally folded forward in the outer quarter. Our specimens were found with Mortoniceras perinflatum, which indicates the ammonite zone.