7-467: See text 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 position; and thus resemble contemporary Psiloceratoidea . Spines, or tubercles, are typically found in two rows on the inner and outer parts of
14-585: 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
21-515: 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
28-799: 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
35-633: 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
42-642: The Treatise 1957 but are now regarded as families in their own right, These are the Phricodoceratidae and Coeloceratidae Genera that have been attributed to the Xiphoceratinae are Bifericeras , Microderoceras , and Xipheroceras . Those attributable to the Eoderoceratinae include Crucilobiceras , Eoderoceras , Neomicroderoceras , and Promicroceras All can be regarded simply as eoderoceratids. This Ammonitina -related article
49-421: The whorl sides, joined by radial ribs. These are often more developed on the inner and middle whorls, becoming less so or absent on the outer. Sutures are highly complex. The Eoderoceratidae can be divided into two subfamilies, the Xiphoceratinae which is the earliest and in which there is an early maximum development of spines of the inner whorls, and the Eoderoceratinae. Two other subfamilies were included in
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