Ammonitina comprises a diverse suborder of ammonite cephalopods that lived during the Jurassic and Cretaceous periods of the Mesozoic Era.

They are excellent index fossils, and it is often possible to link the rock layer in which they are found to specific geological time periods.

Sutures are generally ammonitic, characterized by complex saddle and lobe patterns.

As with the subclass, the closest living relatives of the Ammonitina are the Coleoidea (octopus, squid, and cuttlefish) and not the superficially similar modern Nautilus.

The Cretaceous Desmoceratoidea are derived from the Phylloceratina separately from Jurassic forms and give rise to the Hoplitoidea and to the Acanthoceratoidea.