Eucalycoceras

Eucalycoceras is an extinct genus of cephalopods belonging to the Ammonite subclass.
Description.
"Eucalycoceras" are medium-sized ammonites, generally compressed, with flattened flanks and venter with dense tuberculate ribs.
Distribution.
Fossils of this genus have been found in the Cretaceous of Antarctica, Brazil, France, the United Kingdom and United States.