Ancyloceratina

Ancyloceratina Temporal range: 199.6–64.8 Ma PreꞒ Ꞓ O S D C P T J K Pg N Jurassic - Paleocene
A reconstruction of a heteromorph ammonite, Hamites sp.
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	†Ammonoidea
Order:	†Ammonitida
Suborder:	†Ancyloceratina Wiedmann [de], 1966
Superfamilies
Ancyloceratoidea Douvilleiceratoidea Turrilitoidea Deshayesitoidea Scaphitoidea

The Ancyloceratina were a diverse suborder of ammonite most closely related to the ammonites of order Lytoceratina. They evolved during the Late Jurassic but were not very common until the Cretaceous period, when they rapidly diversified and became one of the most distinctive components of Cretaceous marine faunas. They have been recorded from every continent and many are used as zonal or index fossils. The most distinctive feature of the majority of the Ancyloceratina is the tendency for most of them to have shells that are not regular spirals like most other ammonites. These irregularly-coiled ammonites are called heteromorph ammonites, in contrast to regularly coiled ammonites, which are called homomorph ammonites.