Cretaceous Audoliceras Heteromorph Ammonite

Name: Ammonita; Pleuroceratidae; Audoliceras sp.

Phylum Mollusca, Class Cephalopoda, Subclass Ammonoidea, Order Ammonitida

Geological Time: Cretaceous Aptian Stage (~120 million years ago)

Size (25.4 mm = 1 inch): 205 mm across on a 190 mm by 260 mm base.

Fossil Site: Volga River Region, Saratov, Russia

This is an ammonite of the genus Audoliceras coming from Cretaceous, Aptian Stage (120 m.y.a) deposits of Russia. It has what is known as heteromorph shape. While most ammonites have spiral shells that retain the same shape throughout growth (homomorph), a major group of ammonites, the Ancyloceratina, emerged during the Late Jurassic that had uncoiled shells; they were named heteromorphs, meaning different-shaped. While little is known of their mode of life, their uncoiled shells would have hindered fast swimming. They may have wobbled their way through the water column without spread tentacles, grapping whatever prey came within their reach. As with all other ammonites, the heteromorphs went extinct at the end of the Cretaceous.

Also see: Ammonite Fossils

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