| Measurements | D mm | H/D | T/D | O/D | H/T |
|---|---|---|---|---|---|
| CP-582 | 30.9 | 0.46 | 0.36 | 0.24 | 1.26 |
| Jaffré 2022 p.85 | 34.8 | 0.43 | 0.34 | 0.24 | 1.27 |
| RJ-800 figured | 43.4 | 0.42 | 0.32 | 0.27 | 1.34 |
| Lectotype Casey 1961 | 56 | 0.45 | 0.34 | 0.23 | 1.32 |
| Age | Origin |
|---|---|
|
Grey clay O. subhilli zone Lower Albian |
Mesnil-Saint-Père Aube, France |
Description. Small, pyritic phragmocone with visible sutures. Whorls slightly compressed, with a 60% overlap and a thick elliptical cross-section. The convex flanks diverge slightly to the lower third, then converge towards a broadly rounded venter. Small umbilicus with a rather low wall, quarter-circle in shape. On the last whorl, eight rounded, sigmoid ribs with irregular spacing arise from the umbilical wall. They are bordered anteriorly by a constriction, barely visible at the base of the flanks. Another constriction borders some ribs apically (at 11 o'clock on the lateral view). Ribs and constrictions cross the venter with a proverse sinus. The suture lines are fairly simple but more deeply incised than those of B. (B.) laevigatum. The first lateral lobe, L1, is trifid and slightly asymmetrical.
Remarques. Personal discovery. D'Orbigny's drawing (Paléontologie Française, pl. 81, fig. 6-8) is idealized, with 7 ribs without bordering constrictions but with numerous intermediate riblets. According to Casey (1961, p. 153), the ribs can have a constriction anteriorly, posteriorly, or on both sides, and the umbilical margin can be rounded or angular. In the Aube region, this species is found alongside B. (B.) albense (see its entry) in the subhilli and steinmanni zones, and in the pseudolyelli subzone of the benettianus zone (Lower Albian). It is distinguished by thicker whorls (H/T = 1.26–1.32 vs. 1.43–1.50) and fewer but stronger ribs (5–10 vs. more than 10). Since intermediate forms exist, the two ammonites may be conspecific. Given its rather strong ornamentation, Robert et al. (2001) and Bert (2012) believe that B. dupinianum belongs more closely to genus Uhligella, although it lacks the umbilical tubercles of that genus.