| Measurements | D mm | H/D | T/D | O/D | H/T |
|---|---|---|---|---|---|
| CP-374/60 | 70.1 | 0.34 | 0.40 | 0.33 | 0.85 |
| Saveliev 1992, pl.45 fig.1 | 90 | 0.37 | 0.38 | 0.33 | 0.94 |
| Sinzow, pl.3 fig.4-5 | 90.5 | 0.45 | 0.42 | 0.30 | 1.00 |
| Sinzow, pl.3, fig.6 | 125.5 | 0.40 | 0.45 | -- | 0.89 |
| Age | Origin |
|---|---|
|
sinzowi zone, puzosianus subzone of Mangystau Lower Albian |
North-Aktau Ridge Mangystau Peninsula Kazakhstan |
Description. Ammonite with its white test, featuring a fairly wide umbilicus, whorls overlapping by 45%, and the body chamber on half a whorl. The whorl section is hexagonal with rounded shoulders (the almost quadratic appearance in the photograph is an optical illusion due to the angled break). The umbilical wall is low, at 45°. The 16 umbilical bullae have irregular heights and fall on the umbilical suture, two details also noted by Sinzow. They give rise to raised and sharp ribs in pairs, with much wider interspaces. One unforked rib is often inserted between two successive pairs. In total, 25 ribs cross the venter of the last whorl, with a shallow and wide sinus. This specimen is very similar to those of Sinzow and Saveliev, except for its slightly thicker whorl section.
Remarks. This species known from Mangystau only has not been reviewed since Sinzow's brief diagnosis, and its suture is unknown. In 1952, Casey created Tetrahoplites subquadratus (see its entry) for the Sonneratia subquadrata of plate 3, figs. 7-8 of Sinzow. The S. subquadrata var. sexangula of figs. 4-5 became Sonneratia (Sonneratia) sexangula for Saveliev (1992), while Cooper and Owen (2012) renamed it Tetrahoplites sexangulus. It is true that the species is borderline. It complies with Sonneratia because its flanks are too convergent for a Tetrahoplites, hence its hexagonal whorl section. But the wide and flattened venter, the fairly wide umbilicus, the slightly curved ribs (including very divergent pairs) and the weak ventral sinus suggest Tetrahoplites.