Wähner describes some ammonites that differ from C. rotiforme by lack of keel formation and refers to the similarity with Coroniceras kridion Hehl. Such a fragment is also available to us:
From the typical spines on the ribs, two very faintly raised ribs each seem to pull forward to the external side. This is sharpened like a roof, a true keel is not present. In good condition, it can be seen that the ribs meet externally at an acute angle, making the "keel" appear somewhat wavy.
The cross-section of the coils and the ribbing are, as Wähner describes, very similar to Coroniceras rotiformis.
* Description according to Wähner (1894), supplemented
The spines on the straight ribs together with an indicated keel speak clearly for the genus Coroniceras. Characteristic for C. kridion is the canted external side without a detached keel.
The ammonites from the close relationship of Coroniceras rotiforme have not been found at all in the Karwendel Mountains so far. The illustrated pieces all come from the historical sites in Lower Austria.
- 1894 Arietites rotiformis Sow. var. aff Kridion Hehl – Wähner, S. 216, Taf. 52,5-9