| Measurements | D mm | H/D | T/D | O/D | H/T |
|---|---|---|---|---|---|
| Kennedy et al. 2008 | 49.4 | 0.53 | 0.28 | 0.14 | 2.14 |
| Holotype | 52.5 | 0.53 | 0.24 | 0.16 | 1.76 |
| CP-411 | 65.5 | 0.52 | 0.29 | 0.15 | 1.76 |
| Juignet et al. 1976 | 79.5 | 0.54 | 0.25 | 0.08 | 2.21 |
| Kennedy et al. 2008 | 90 | 0.49 | 0.35 | 0.19 | 1.40 |
| Age | Origin |
|---|---|
|
Sandy clay perinflatum zone Upper Albian |
Kolbay promontory East of Mangystau Kazakhstan |
Description. Internal mold of a brown phosphate phragmocone, with whorls 90% covered and the last eighth of whorl corroded. Small, funnel-shaped umbilicus, rather shallow, clearly exposing the inner whorls, with a straight 60° slope and a very narrowly rounded margin. The section of maximum thickness at the umbilical margin is triangular, with slightly convex flanks and the apex truncated by a narrow venter, forming a smooth band with angular shoulders. The flanks are also smooth, without tubercles. However, in raking light, 18 flattened ribs are discernible, reduced to vague, concave crescents on the outer half of the flanks. The suture line is quite peculiar. It has low, frilled elements with, from the siphonal line to the umbilical suture, 6 saddles with a median incision and 5 lobes constricted at the base. The third lateral lobe (first auxiliary lobe) is clearly bifid and bigger than the other lobes. The second auxiliary lobe is smaller than the third.
Remarks. Sokolov (1967) created the genus Karamaiceras for this species from the Kolbay promontory in Mangystau, hence the name. Mirzoev (1967) described the evolution of the suture line. In their revision of the Placenticeratidae, Klinger & Kennedy (1989) consider this genus a synonym of Placenticeras. Kennedy et al. (2008) describe the Albian-Cenomanian boundary at Kolbay and illustrate several specimens, which are abundant in a Vraconian bed (late Albian). They emphasize its great variability: specimens like ours are compressed and smooth, then with age they thicken, the venter widens, and small umbilical and ventrolateral tubercles appear, especially on the body chamber. Only one specimen was discovered in France, during a survey in Sarthe (Juignet et al., 1983).