Eoderoceratoidea is a superfamily of true ammonites (suborder

Ammonitina Ammonitina comprises a diverse suborder of ammonite cephalopods that lived during the Jurassic and Cretaceous periods of the Mesozoic Era. They are excellent index fossils, and it is often possible to link the rock layer in which they are found t ...

) from the Lower

Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

, comprising seven phylogenetically related families, characterized in general by having ribbed evolute shells that commonly bear spines or tubercles. Adult shell size ranges from 2 or 3 cm to giants reaching 50 cm in such genera as ''

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 ' ...

'', '' Epideroceras'', and '' Liparoceras''.Donovan,D.T., Callomon and Howarth 1981. Classification of the Jurassic Ammonitina; Systematics Association. Arkell ''et al.'', 1957. Mesozoic Ammonoidea, in Treatise on Invertebrate Paleontology, (Part L); Geological Soc. of America and University of Kansas press The earliest known eodoceroceratoidean is the eoderoceratid genus '' Microderoceras''. Although its origin is uncertain, it is likely that it is derived from the

Psiloceratoidea Psiloceratoidea is a superfamily of Early Jurassic ammonoid cephalopods proposed by Hyatt in 1867, assigned to the order Ammonitida. They were very successful during Hettangian and Sinemurian. Last of them, family Cymbitidae and genera '' Hypox ...

. It has also been proposed, with some imagination, that ''Microderoceas'' has its origin some earlier Jurassic lytoceratid such as '' Analytoceras''. Seven families are included, beginning with the Eoceroceratidae, which gave rise at about the same time to the Phricodoceratidae, Coeloceratidae, Liparoceratidae, and Polyhmorphitidae. The Phricodoceratidae left no descendants but the Coeloceratidae later gave rise to the Dactylioceratidae and the Liparoceratidae to the Amaltheidae. The Polymorphitidae became the source for the superfamilies Hildocerataceae beginning with the Hildoceratidae. The more recent taxonomy of Donovan et al. (1981) with seven families, differs from that of Arkell, et al. in the Treatise (1957) which included just five families. The phricodoceratids and coeoloceratids were then considered as subfamilies (Phricodoceratinae and Coeloceratinae, respectively) of the Eoderoceratidae. As later (1981) the Liparoceratidae and Polyhmorphitidae were derived from the Eoderoceratidae but the Dactylioceratidae were derived separately (1957) from the Lytoceratidae - a source since then largely rejected.

References

Ammonitida superfamilies Jurassic ammonites Early Jurassic first appearances Early Jurassic extinctions {{Ammonitina-stub