Anisoceratidae is an extinct

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

of heteromorph

ammonites Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...

which belong to the

Ancyloceratina 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 beca ...

superfamily

Turrilitoidea Turrilitoidea is a diverse superfamily of Cretaceous ammonites generally considered as heteromorphic and commonly included in the suborder Ancyloceratina. Shells of this diverse group do not coil planospirally, as typical for most ammonitida, am ...

. Members of the family range is from the lower

Albian The Albian is both an age (geology), age of the geologic timescale and a stage (stratigraphy), stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early Cretaceous, Early/Lower Cretaceous epoch (geology), Epoch/s ...

to the upper

Turonian The Turonian is, in the International Commission on Stratigraphy, ICS' geologic timescale, the second age (geology), age in the Late Cretaceous epoch (geology), Epoch, or a stage (stratigraphy), stage in the Upper Cretaceous series (stratigraphy), ...

. The family is possibly derived from a member of the

Hamitidae ''Hamites'' (" hook-like") is a genus of heteromorph ammonite that evolved late in the Aptian stage of the Early Cretaceous and lasted into the Cenomanian stage of the Late Cretaceous. The genus is almost certainly paraphyletic but remains in wi ...

Morphology

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.

History and classification

Older classifications, since first publication of Part L of the

Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authore ...

, 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 Turrilitina is a proposed suborder of Cretaceous heteromorph ammonoid cephalopods derived from the Lytoceratidae in the Hauterivian stage of the Lower Cretaceous that would include the superfamilies Turrilitoidea, Ptychoceratoidea, and Scapha ...

, 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
Cretaceous ammonites Ammonitida families Turrilitoidea Albian first appearances Turonian extinctions {{Ammonitida-stub