Large Heteromorph Crioceras Ammonite Pair on Matrix

Crioceras loryi

Ammonoidea, Oxynoticeratidae

Geological Time: Lower Cretaceous, Hauterivian Stage (~133 million years ago)

Size (25.4 mm = 1 inch): Ammonite is 88 mm across on a 110 mm by 120 mm base, Drome, France

Code: FA05

Price: $135.00


Heteromorph Crioceras AmmoniteDescription: A fine example of an ammonite of the genus Crioceras of the Hauterivian Stage (135 m.y.a) deposits of France. It has what is known as heteromorphic shape. While most ammonites have spiral shells that retain the same shape throughout growth (homomorph), a major group of ammonites, the Ancyloceratina, Heteromorph Ammoniteemerged during the Late Jurassic which had uncoiled shells instead, and were called herteromorph ammonites (different-shaped). While little is known of their mode of life, their uncoiled shells would have precluded fast swimming. They may have wobbled their way through the water column with out-splayed tentacles, sweeping whatever came within their reach into their hungry mouths. As all ammonites, these went extinct at the end of the Cretaceous.

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