| Species | Discamphiceras guidonii (SOWERBY) |
| Author | SOWERBY |
| Group | Psiloceraten |
| Horizon | atanatense-horizon |
| Zone | marmoreum-zone |
| Stage | Upper Hettangian |
Description
A particularly strong nodule stage is formed on the innermost coils. These nodules flatten and merge into s-shaped ribs, with irregularly appearing cleavage and switching ribs. The ribs are still weak on the inner side, on the middle of the flank the switching ribs become increasingly distinct, towards the outer side the ribs are strongest, stand there regularly and even overlap. This regular ribbing on the outer side can be followed for quite a long time. With increasing size the external side remains unribbed at some point. Most specimens of D. guidonii are small; those with a diameter of more than 50mm are very rare. At this size the sculpture is hardly distinguishable from that of D. atanatense. The navel width, which is clearly smaller in D. guidonii, is unambiguous. The winding cross-section is highly oval, with a distinct umbilical edge. The umbilical wall is vertical and the external side broadly rounded.
* Description according to WÄHNER, supplemented
Compare
The strong sigmoidal ribbing makes this species very easy to identify. According to Wähner, Sowerby's characterisation of D. guidonii is extremely poor or incorrect. We do not consider a separation of the later established species D. emmrichi necessary. It is probably one and the same variable species. Wähner discusses this in detail.
Large specimens can only be distinguished from D. atanatense by close observation. The ribbing is somewhat stronger and the navel width smaller than in D. atanatense. The next following genus with an even narrower umbilicus would be Metamorphites (Kment 2000).
Interestingly, there are very rare specimens that fall somewhere in between (e.g. Discamphiceras (Kammerkaroceras) sp. in Kment 2000).
Dimension
Dimensions at D= 19mm (according to Kment):
Nw % v. D: ca. 21%
Wh % v. D: ca. 48%
Wb % v. D: ca. 28-31%
—
Abmessungen bei D= 59mm (nach Kment):
Nw % v. D: ca. 14%
Wh % v. D: ca. 50%
Wb % v. D: ca. 24%
Literature
- 1883 Aegoceras n.f.ind. – WÄHNER S. 27, Taf. 14.2
- 1884 Aegoceras emmrichi Guemb.- WÄHNER S. 53, Taf. 26.4-6
- 1884 Aegoceras guidonii Sowerby- WÄHNER S. 60, Taf. 26.3,7
- 1993 Kammerkaroceras guidonii Guembel- Rakus & Lobitzer S. 925, Taf. 1.6-9
- 2000 Discamphiceras (Kammerkaroceras) guidonii Sowerby – Kment S. 198, Taf. 2.6
