Coeloceratidae is a family of ammonites belonging to the

Eoderoceratoidea Eoderoceratoidea is a superfamily of true ammonites (suborder Ammonitina) from the Lower Jurassic, comprising seven phylogenetically related families, characterized in general by having ribbed evolute shells that commonly bear spines or tubercle ...

that lived during the

Early Jurassic The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...

. Shells are evolute, tending to be broadly discoidal with depressed whorls bearing primary and secondary ribs that branch from outer lateral tubercles. Most of the included species have coronate inner whorls and outer tubercles only. In general, Coeloceratids resemble the

Middle Jurassic The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively rare, but geological formations co ...

Stephanoceras ''Stephanoceras'' (meaning ''crown horn'') is an extinct genus of Stephanoceratoid ammonite which lived during the Bajocian (Middle Jurassic). It is the type genus of the family Stephanoceratidae. Type species ''Ammonites humphriesianum'' J. ...

''. Once regarded as the subfamily Coeloceratinae in the

Eoderoceratidae Eoderoceratidae is the ancestral and most primitive family of the Eoderoceratoidea; lower Jurassic ammonite cephalopods, characterized by evolute, commonly serpenticonic, shells that had long body chambers and would have had no stable floating ...

, these ammonites are now given familial rank. Genera included in the Coeloceratidae are '' Coeloceras'', ''

Apoderoceras ''Apoderoceras'' is an extinct genus of cephalopod belonging to the ammonite subclass. Biostratigraphic significance The International Commission on Stratigraphy (ICS) has assigned the First Appearance Datum of genus ''Apoderoceras'' and of '' ...

'' '' Coeloderoceras'', '' Hyperderoceras'', '' Pimalites'', '' Praesphaeroceras'', and '' Tetraspidoceras''. ''Tetraspidoceras'', which is bituberculate, is a possible ancestral member of the family. The Coeloceratidae give rise to the

Dactylioceratidae The family Dactylioceratidae comprises Early Jurassic ammonite genera with ribbed and commonly tuberculate shells that resembled later Middle Jurassic stephanoceratids and Upper Jurassic perisphinctids. Shells may be either evolute or involu ...

References

* Arkell ''et al.'', 1957. Mesozoic Ammonoidea, in Treatise on Invertebrate Paleontology, (Part L); Geological Soc. of America and University of Kansas press. * Donovan, Callomon, and Howarth 1981. Classification of the Jurassic Ammonitina; Systematics Association

Ammonitida families Eoderoceratoidea Jurassic ammonites Hettangian first appearances Early Jurassic extinctions {{Ammonitina-stub