Anisoceratidae

Anisoceratidae Temporal range: Albian–Turonian PreЄ Є O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Ammonoidea
Order:	Ammonitida
Suborder:	Ancyloceratina
Superfamily:	Turrilitoidea
Family:	Anisoceratidae
Genera
Allocrioceras Anisoceras Idiohamites Protanisoceras

Anisoceratidae is an extinct family of heteromorph ammonites which belong to the Ancyloceratina superfamily Turrilitaceae. Their range is from the lower Albian to the upper Turonian. The family is possibly derived from a member of the Hamitidae.

Anisoceratid shells begin as an irregular helical spiral which typically becomes confined to a single plane with growth. This is usually followed by at least a single straight shaft. Ribs and tubercles are common features.

Older classifications, since first publication of Part L of the Treatise on Invertebrate Paleontology, include the Anisoceratidae in the suborder Ancyloceratina (within the Turrilitoidea). Subsequent study, e.g. Beznosov & Mikhailova 1983, has suggested that the Turrilitoidea, including the Anisoceratidae, have a different phylogeny from the true Ancyloceratina, resulting in their occasional reassignment to a separate suborder, the Turrilitina, however this classification is not widely followed.

References

• Beznosov & Mikhailova 1983 referenced in A. Mikhailova and E. Yu. Baraboshkin, 2009. The Evolution of the Heteromorph and Monomorph Early Cretaceous Ammonites of the Suborder Ancyloceratina Wiedmann. Paleontological Journal, Vol. 43, No. 5, 2009.
• The Paleobiology Database Anisoceratidae entry