6-630: Coeloceratidae is a family of ammonites belonging to the Eoderoceratoidea that lived during the Early Jurassic . 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 Stephanoceras . Once regarded as
12-515: Is the eoderoceratid genus Microderoceras . Although its origin is uncertain, it is likely that it is derived from the Psiloceratoidea . 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
18-727: The Dactylioceratidae This Ammonitina -related article is a stub . You can help Misplaced Pages by expanding it . 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 tubercles. Adult shell size ranges from 2 or 3 cm to giants reaching 50 cm in such genera as Apoderoceras , Epideroceras , and Liparoceras . The earliest known eodoceroceratoidean
24-799: 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
30-633: 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. This Ammonitina -related article
36-459: The subfamily Coeloceratinae in the Eoderoceratidae , these ammonites are now given familial rank. Genera included in the Coeloceratidae are Coeloceras , Apoderoceras Coeloderoceras , Hyperderoceras , Pimalites , Praesphaeroceras , and Tetraspidoceras . Tetraspidoceras , which is bituberculate, is a possible ancestral member of the family. The Coeloceratidae give rise to
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