- Audoliceras sp. (Heteromorph) & Deschaisites Ammonites
- Cretaceous Age
- Ulyanovsk River Region
- This is a beautiful specimen.. it is like a piece of art! Both ammonites were prepped free from their original crumbling matrix and set into this other piece of matrix. They are genuine ammonites. The overall size of the matrix is approx. 10 3/4″ x 17 3/4″. The Audoliceras measures approx. 8 1/2″ long in a straight line measurement, and the Deschaisites measures 3 1/2″ wide. There is also a TINY ammonite on the edge of the matrix.. very cute!!
These irregularly-coiled ammonites are called heteromorph ammonites, in contrast to regularly coiled ammonites, which are called homomorph ammonites. The biology of the heteromorph ammonites is not clear, but one certainty is that their uncoiled shells would have made these forms very poor swimmers. Open shells, particularly ones with spines and ribs, create a lot of drag; but more importantly, the orientation of the shell, with the body hanging below the buoyant part of the shell, would have created a serious impediment to efficient swimming. It’s more likely these ammonites either drifted in the plankton, collecting small animals on long tentacles like
modern jellyfish, or else they crawled along the sea floor feeding on sessile or slow-moving animals such as clams.