| Species | Megastomoceras pleurolissum (WÄHNER) |
| Author | WÄHNER |
| Group | Psiloceraten |
| Horizon | curviornatum-horizon |
| Zone | megastoma-Zone |
| Stage | Middle Hettangian |
Description
The cross-section of the windings is oval, the umbilical drop is relatively broadly rounded, the outer side as well. The coils reach their greatest thickness approximately in the middle of the curved flank. Characteristic is the ribbing, which is very weak on the inner coils and disappears with increasing size.
The involution is quite high.
The species is obviously extremely rare and also large in size.
* Description according to Wähner (1883), supplemented
Compare
At first glance, you think you have found a Psiloceras strongolum.
However, due to the deviating dimensions (especially the navel width is smaller) M. pleurolissum is different from the known psilocerates. The higher stratigraphic level also speaks against Psiloceras.
According to Wähner, only M. aphanoptychum is very similar, which is also only very weakly ribbed and possibly identical. Since only one specimen of each species was available, this question could not be clarified. The specimen illustrated here does not allow any conclusions either. The innermost coils are not preserved.
Dimension
Dimensions with D= 130mm
Nw % v. D: ca. 50%
Wh % v. D: ca. 27%
Wb % v. D: ca. 18%
Literature
- 1883 Aegoceras pleurolissum n.f. – Wähner, S. 123, Taf. 14,4
