Cardioceras

Cardioceras is an extinct ammonite genus belonging to the family Cardioceratidae. These fast-moving nektonic carnivores lived during the Jurassic period, Oxfordian age.

Description
Shells of Cardioceras species can reach a diameter of 20 - 25 mm. The shape is circular, with ribs and a prominent ridge along the dorsal edge.

Distribution
Fossils of species within this genus have been found in the Jurassic of France, Germany, Poland, Russia, the United Kingdom and Alaska.