Eoderoceratidae
Encyclopedia
The Eoderoceratidae is the ancestral and most primitive family of the Eoderocerataceae
; 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 Psilocerataceae
. Spines, or tubercles, are typically found in two rows on the inner and outer parts of 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 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 Xiphoceras. Those attributable to the Eoderoceratinae include Crucilobiceras
, Eoderoceras
, Metaderoceras
, Neomicroderoceras, and Promicroceras
All can be regarded simply as eoderoceratids.
Eoderocerataceae
Eoderocerataceae is a superfamily of true ammonites from the Lower Jurassic, comprising seven phylogenetically related families, characterized in general by having ribbed evolute shells that commonly bear spines or tubercles...
; lower Jurassic ammonite
Ammonitida
The Ammonitida is an order of more highly evolved ammonoid cephalopods from the Jurassic and Cretaceous time periods, commonly with intricate ammonitic sutures....
cephalopods, characterized by evolute, commonly serpenticonic, shells that had long body chambers and would have had no stable floating position; and thus resemble contemporary Psilocerataceae
Psilocerataceae
The Psilocerataceae is a superfamily of Early Jurassic ammonoid cephalopods proposed by Alpheus Hyatt in 1867, assigned to the order Ammonitida....
. Spines, or tubercles, are typically found in two rows on the inner and outer parts of 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 the Treatise 1957 but are now regarded as families in their own right, These are the Phricodoceratidae
Phricodoceratidae
Phricodoceratidae is a family in the Eoderocerataceae, aberrant ammonites from the Lower Jurassic characterized by a large adult size and a marked change of shell form and ornament with growth...
and Coeloceratidae
Coeloceratidae
Coeloceratidae is a family of ammonites belonging to the Eoderocerataceae] 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...
Genera that have been attributed to the Xiphoceratinae are Bifericeras
Bifericeras
Bifericeras is a Lower Jurassic ammonite beloning to the family Eoderoceratidae, and sometimes placed in the subfamily Xipherceratinae. Whorls are strongly depressed, but still evolute in coiling...
, Microderoceras
Microderoceras
Microderoceras is a flat sided, evolute, radially ribbed Lower Jurassic ammonite belonging to the ammonitid family Eoderoceratidae and superfamily Eoderocerataceae...
, and Xiphoceras. Those attributable to the Eoderoceratinae include Crucilobiceras
Crucilobiceras
Crucilobiceras is an ammonoid cephalopod genus from the Lower Jurassic belonging to the eoderoceratacean family Eoderoceratidae. Cruciliboceras has an evolute shell, such that all whorls are well exposed, with persistent radial ribbing and with spines or tubercles on the outer, ventral, rim, and...
, Eoderoceras
Eoderoceras
Eoderoceras is an evolute, round whorled ammonite from the Lower Jurassic with an outer row of distinct spines, and in some, an inner row of tubercles, on either side; ribs only on the inner whorls....
, Metaderoceras
Crucilobiceras
Crucilobiceras is an ammonoid cephalopod genus from the Lower Jurassic belonging to the eoderoceratacean family Eoderoceratidae. Cruciliboceras has an evolute shell, such that all whorls are well exposed, with persistent radial ribbing and with spines or tubercles on the outer, ventral, rim, and...
, Neomicroderoceras, and Promicroceras
Promicroceras
Promicroceras is an extinct ammonite genus from the upper Sinemurian of Europe, named by Leonard Spath in 1925. Promicroceras is included in the family Eoderoceratidae, which is part of the ammonitid superfamily Eoderocerataceae. The type is P...
All can be regarded simply as eoderoceratids.