Phylloceras

Phylloceras is an extinct genus of ammonoid cephalopods belonging to the family Phylloceratidae. These nektonic carnivores lived from Early Jurassic (Hettangian age) to Late Cretaceous (Maastrichtian age) (from 201.30 to 66.043 Ma).
Description.
Shells of "Phylloceras" can reach a diameter of about , with a maximum of about . These primitive ammonites had an involute, laterally flattened shell with a regular shell opening. They were almost smooth and the ornamentation was virtually absent or, at most, represented by simple growth lines barely visible. The striking sinuous suture lines were characteristic of this genus. They are reminiscent, in some ways, of the leaves of plants (hence the name "Phylloceras", which means " leaf-horn").
Distribution.
Fossils of species within this genus have been found all over the world, particularly in Western Europe.