The Crioceratidae constitute a family of loosely to closely coiled Ammonitida included in the Ancyloceratoidea that lived during the Early Cretaceous; characterized by '' Crioceratites'' and other genera such as '' Hoplocrioceras'' and '' Paracrioceras''. The Crioceratidae are gyroconic, coiled in a plane, generally with space between the whorls although in some like ''

Balearites ''Balearites'' is an extinct ancyloceratin genus included in the family Crioceratitidae, subclass Ammonoidea, from the Upper Hauterivian. The shell, or conch, of ''Balearites'' is planispiral; whorls compressed, fairly flat sided, barely in co ...

'' the whorls are barely in contact. Although distinct in character and not truly heteromorphic the Crioceratidae were included in the American

Treatise A treatise is a formal and systematic written discourse on some subject, generally longer and treating it in greater depth than an essay, and more concerned with investigating or exposing the principles of the subject and its conclusions."Treat ...

Part L, 1957, in the

Ancyloceratidae Ancyloceratidae is a family of heteromorphic Ammonitida, ammonites that lived during the Early Cretaceous. Their shells begin as a loose spiral with whorls not touching which then turns into a straight shaft that ends in a J-shape hook or bend ...

as the subfamily Crioceratinae. It is now considered a distinct family as originally proposed by Wright 1952 with the

Acrioceratidae Acrioceratidae is a family of heteromorph ammonites included in the Ancyloceratoidea comprising ancyloceratid-like forms that start off with a coiled juvenile section, followed by a straight or curved shaft ending in a hook. Two described gener ...

, proposed by Vermeulen (2004), a transition between the two. Other genera in the Crioceratidae include '' Aegocrioceras'', '' Menutheocrioceras'', and '' Shasticrioceras''.

References

* W.J. Arkell, et al., 1957. Mesozoic Ammonoidea; Treatise on Invertebrate Paleontology, Part L, Mollusca 4. Geological Society of America and University of Kansas Press. Cretaceous ammonites {{ammonite-stub