Fine Aegocrioceras Heteromorph Ammonite

Aeogocrioceras spathi

Ammonita, Ancyloceratidae

Geological Time: Lower Cretaceous, Hauterivian Stage (~135 million years ago)

Size (25.4 mm = 1 inch): 62 mm across by 52 mm tall

Fossil Site: Resse Pit, Hannover, Germany

Code: GF09

Price: $235.00


Aegocrioceras Heteromorph AmmoniteDescription: A fine example of an ammonite of the genus Aegocrioceras of the Hauterivian Stage (135 m.y.a) deposits of Germany. 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 which had uncoiled shells instead, and were called heteromorph ammonites (different-shaped). This one has the cyrtocone form in which the coils do not touch, forming an open spiral. 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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