Perisphinctes

phylum	Mollusca	The extinct genus Perisphinctes is an ammonite cephalopod that serves as an index fossil for the middle to late Jurassic. Some specimens could reach an enormous size, as large as 3.3 feet. Fossil locations indicate a wide distribution from Europe to Antarctica, and from South America to Asia. For more information, visit the Wikipedia entry. Get back to Ammonites
class	Cephalopoda
order	Ammonitida
family	Perisphinctidae
genus	Perisphinctes

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  Geoworld Ammonite