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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''.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 ve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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''.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 ve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coeloceratidae
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 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 the Dactylioceratidae The family Dactylioceratidae comprises Early Jurassic ammonite genera with ribbed and commonly tuberculate shells that res ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 involute. Description Ammonites with evolute, serpenticone to cadicone shells with ribs, sometimes with tubercules. Members of this family had no keels. while homeomorphic with stephanoceratids and perisphinctids, they had unique shell structure with double shells and flat-topped ribs on the inner shell. Based on suture differences, they are divided into 2 subfamilies. Reynesocoeloceratinae possess two major secondary lobes in dorsal side of external saddle. This saddle is not divided this way in Dactylioceratinae, while lateral lobe is deeply trifid. Evolution It has been suggested, that this family is polyphyletic, but this is now considered to be false. Reynesocoeloceratinae evolved in lower Pliensbachian from '' Metaderoceras'' and died o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 position; and thus resemble contemporary Psiloceratoidea. 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phricodoceratidae
Phricodoceratidae is a family in the Eoderoceratoidea, aberrant ammonites from the Lower Jurassic characterized by a large adult size and a marked change of shell form and ornament with growth. Shells are stoutly ribbed, early growth stage is round-whorled with spines, followed by a high-whorled late growth stage with smooth, modified ribbing. Three genera are currently placed in the Phricodoceratidae: '' Phricodoceras'', '' Epideroceras'', and '' Pseuduptonia''. References *Arkell ''et al.'', 1957. Mesozoic Ammonoidea, in Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology'' (or ''TIP'') published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and co ..., (Part L); Geological Soc. of America and University of Kansas press. *Donovan, Callomon, and Howarth 1981 Classification of the Jurassic Ammonitina; Systematics Association ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymorphitidae
Polymorphitidae is a family of Early Jurassic ammonoid cephalopods that contribute to the Eoderoceratoidea. Two subfamilies, the Polymorphtinae and Tropidoceratinae, are included. Polymorphitid ammonites produced typically evolute shells, which are more compressed than in most members of the superfamily. Many possess ventral chevrons and/or a fastigate venter resembling a gable roof, which in some develops into a true keel on the outer whorls. The Polymorphtinae is the larger and more diverse subfamily of the two. their shells have venters (outer rims) that may be smooth or ribbed, or have a median row of beading or serrations. The Tropidoceratinae, referred to as the Acanthopleuroceratinae in the Treatise A treatise is a formal and systematic written discourse on some subject, generally longer and treating it in greater depth than an essay, and more concerned with investigating or exposing the principles of the subject and its conclusions."Treat ... L 1957, instead hav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 to specific geological time periods. The shells of Ammonitina are typically planospiral; coiled in a plane, symmetrical side to side. Shells vary in form, including those that are evolute, such that all whorls are exposed, and those that are strongly involute with only the outer whorl showing. They may be strongly ribbed, some bearing nodes and spines; others are entirely smooth. Some have broad rounded venters (the outer rim); in others the venter is sharp and keel-like. Sutures are generally ammonitic, with intricately patterned saddle and lobes. However, in some derived forms the suture becomes simplified, ceratitic, even goniatitic. The Ammonitina are derived from the Phylloceratina, another ammonitid suborder which has its origin in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hildocerataceae
Hildoceratoidea, formerly Hildoceratacaea, is a superfamily of compressed or planulate ammonites, some tending to develop acute outer rims; generally with arcuate or sigmoidal ribs. Aptichus were found in place are double-valved.Arkell ''et al.'', Treatise on Invertebrate Paleontology, Part L Ammonoidea, (1956) Hildoceratoidea is an upper Lower to lower Middle Jurassic group belonging to the Ammonitina that unites the Hildoceratidae, Hammatoceratidae, Graphoceratidae, and Sonniniidae. In some taxonomies the name Phymatoceratidae is substituted for the Hammatoceratidae Hildoceratidae, which is the ancestral family, is derived from the Acanthopleuroceratinae, a subfamily in the Eoderoceratoidean family, Polyorphitidae. The Stephanoceratoidea, Perisphinctoidea, and Haploceratoidea Haploceratoidea, formerly Haplocerataceae, is an extinct superfamily of Ammonoidea, ammonoid cephalopods belonging to the Ammonitida that unites three families, Strigoceratidae, Oppeliidae, and Haplocer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Liparoceratidae
Liparoceratidae is a family of eoderoceratoidean ammonites from the Lower Jurassic that combines genera with a variety of forms including dimorphs that change from one form to another during ontogeny. Three genera and six subgenera are included in the Liparoceridae according to D.T. Donovan in Donovan ''et al.'' 1981; '' Liparoceras'' including ''L''. (''Liparoceras''), ''L''. (''Becheiceras''), and ''L''. (''Vicininodiceras''); '' Aegoceras'' including ''A''. (''Aegoceras''), ''A''. (''Beaniceras''), and ''A''. (''Oistoceras''); and '' Androgynoceras''. Arkell, ''et al.'' (1957) in the Treatise on Invertebrate Paleontology, Part L list ''Liparoceras'' with ''Becheiceras'' and ''Vincininodiceras'' along with '' Parinodiceras'' separately as subgenera; ''Beaniceras'', '' Metacymbites'', ''Oistoceras'', and '' Platynoticeras'' but leave out ''Aegoceras''. ''Parinodiceras'' and its equivalent, '' Platynoticeras'' are removed (Donovan 1981) to the Polymorphitidae. ''Metacymbites' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 '' Bifericeras donovani'' the defining biological marker for the start of the Pliensbachian Stage of the Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), 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 J ..., 190.8 ± 1.0 million years ago. Distribution Jurassic of Argentina, Hungary, Italy, Portugal, the United Kingdom References Eoderoceratoidea Ammonitida genera Jurassic ammonites of Europe Pliensbachian life {{Ammonitina-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amaltheidae
Amaltheidae is a family of eoderoceratoidean ammonitids from the Lower Jurassic consisting of genera characterised by stigated discoidal oxycones—narrow involute shells with narrowly rounded to angular venters that bear a series of grooves, or ridges, along broad flanks, which according to the Treatise L, 1957, evolved into strongly ribbed planulates (discoidal evolute shells) with quadrate whorls, typically with crenulated keels; involving all together four genera. Donovan in Donovan ''et al.'' (1981) retains the Amaltheidae in the sense of Arkell, ''et al.'' 1957, as shown in the Treatise but synonymizes ''Pseudoamaltheus'' with ''Amaltheus'', (a subgenus in the Treatise), reducing the number of valid genera to three. These are ''Amaltheus'', ''Amauroceras'', and '' Pleuroceras''. ''Amaltheus'' is oxyconic, keeled, strigated, and ribbed on the outer flanks. ''Amauroceras'' is smooth, compressed, without ribs or stigation, and the keel is reduced. '' Pleuroceras'' has a pl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microderoceras
''Microderoceras'' is a flat sided, evolute, radially ribbed Lower Jurassic ammonite belonging to the ammonitid family Eoderoceratidae and superfamily Eoderoceratoidea. Its whorls are subquadrangular in section; venter on the outer rim, rounded; sides with two rows if distinct spines, tubercles on internal molds, formed at either end of the ribs. The lateral surface of the ribcage is concave toward both sides, the lateral side of the dorsal and the lateral side of the ventral surface. The ribs are divided into six pairs (1-3) of the following types: 2-3 is the only type. In the first type, the ribs on the ventral face are fused to the ribs on the ventral sides; the ribs on the dorsal face are fused to the ribs on the dorsal sides. The second type represents the ribbed body, the ribs are in the same arrangement as in the first type and the rib cage does not fuse to the dorsal surface. These shelled cephalopods, named by Alpheus Hyatt in 1871, are part of the now extinct Ammonoid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
