| Measurements | D mm | H/D | T/D | O/D | H/T |
|---|---|---|---|---|---|
| Holotype | 40 | 0.48 | 0.32 | 0.19 | 1.50 |
| CP-572 | 45.7 | 0.47 | 0.29 | 0.18 | 1.61 |
| Spath 1925 pl.12 fig.10 | 94 | 0.43 | 0.27 | 0.22 | 1.59 |
| Age | Origin |
|---|---|
|
Grey clay, bed VII D. biplicatus zone Middle Albian |
Folkestone Kent England |
Description. A fine pyritic phragmocone identified by Francis Amédro, with compressed whorls 60% covered and a pearly test. The flat flanks diverge a bit up to mid-flank, then converge, remaining flat, towards a slightly concave venter. The narrow umbilicus has a low wall sloping at 60°, passing to the flank via a rounded edge bearing 14 small, elongated, proverse bullae. The flanks are quasi-smooth at the beginning of the last whorl, then the bullae appear and strengthen progressively, forming bundles of 3 or 4 extremely thin ribs. Generally, two of these ribs terminate in two successive ventrolateral clavi, initially oblique to the siphonal line, then parallel and higher on the last quarter of whorl. The clavi alternate on either side of venter. The other ribs in the bundle are attenuated above the inner third of the flanks, but some persist and join one of the clavate ribs to form a lautiform pair.
Remarks. According to Spath (1925), the juvenile resembles A. planus, then it develops lower whorls, a broader and slightly concave venter, more convex flanks, more prominent umbilical bullae, and bundles of 3-4 ribs that generally join in pairs on the clavi. However, his specimen (pl. XII, fig. 10) does not show lautiform ribs, and the poor illustrations by Sowerby have few of them. The species forms a transition to Dimorphoplites glaber according to Hadland (2018, p. 74), who illustrates two fine specimens from Folkestone. In the same ammonite zone, Anahoplites daviesi Spath, 1925 (see its entry), also has a young stage of the planus type but it is more compressed, less involute, and with non-lautiform ribs and small, oblique clavi.