| Measurements | D mm | H/D | T/D | O/D | H/T |
|---|---|---|---|---|---|
| Holotype | 24 | 0.38 | 0.46 | 0.29 | 0.82 |
| CP-275 | 25.7 | 0.46 | 0.60 | 0.21 | 0.78 |
| Age | Origin |
|---|---|
|
Base of Pénzeskút marls Condensed Upper Albian rostratum to perinflatum zones |
Tilos forest Village of Pénzesgyõr Bakony Hills, Hungary |
Description. A small, very thick ammonite with its test, showing no visible sutures. The whorls, with a depressed reniform section and a very broad venter without shoulders, overlap by 90% but show a tendency to uncoil on the last half-whorl. The maximum thickness is reached at the umbilical edge. The umbilicus is small, deep, and funnel-shaped, with a wall that quickly transitions to the flank via a narrowly rounded edge. This edge bears 11 small umbilical bullae, each giving rise to 1 (or 2 for the last 3 bullae) prominent, straight or slightly concave, somewhat rursiradiate ribs. Triangular in cross-section, they reach their maximum height on venter, which they traverse in a straight line, with a steeper anterior slope than posterior one. The intercostal spaces become wider than the ribs on the last half-whorl. Including 3 shorter, untuberculate intercalary ribs, there are 17 ribs in total on venter.
Remarques. Our specimen conforms to the description of Jattiot et al. (2021, p. 29). These authors add that a rib originating from an umbilical bulla can end up as an intercalary rib on the other flank, and that the ribs weaken or disappear at maturity. Intraspecific variability is important: their measurements on 13 specimens from Salazac (Gard) yield H/D = 0.38–0.49, T/D = 0.40–0.75, O/D = 0.16–0.29, H/T = 0.65–0.97. Rib density is also variable. Numerous specimens are illustrated in Wright & Kennedy (1979), Szives (2007, pl. 14, 16, 20), and Jattiot et al. (2021, fig. 12). In general, their ribs are more rounded, but some specimens show sharper ribs, like ours: see for example Szives, 2007, pl. 16, fig. 7 and 10.