Apoderoceras

Apoderoceras is an extinct genus of cephalopod belonging to the ammonite subclass.

Ammonites (Apoderoceras) were predatory mollusks that resembled a squid with a shell. These cephalopods had eyes, tentacles, and spiral shells. They are more closely related to a living octopus, though the shells resemble that of a nautilus. True ammonites appeared in the fossil record about 240 million years ago. The last lineages disappeared 65 million years ago at the end of the Cretaceous.

Biostratigraphic significance
The International Commission on Stratigraphy (ICS) has assigned the First Appearance Datum of genus Apoderoceras and of Bifericeras donovani the defining biological marker for the start of the Pliensbachian Stage of the Jurassic, 190.8 ± 1.0 million years ago.

Distribution
Jurassic of Argentina, Hungary, Italy, Portugal, the United Kingdom