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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. It has also been proposed, with some imagination, that ''Microderoceas'' has its origin some earlier Jurassic Lytoceratina, lytoceratid such as ''Analy ... [...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 References * Arkell ''et al.'', 1957. Mesozoic Ammonoidea, in Treatise on Invertebrate Paleontology The ''Treatise on In ... [...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 ou ... [...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,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authore ..., (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 Formality, formal and systematic written discourse on some subject concerned with investigating or exposing the main principles of the subject and its conclusions."mwod:treatise, Treatise." Merriam-Webster Online Dictionary. Acc ... L 1957, instead ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonitina
Ammonitina comprises a diverse suborder of Ammonoidea, 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 Geologic time scale, geological time periods. The shells of Ammonitina are typically planospiral, coiled in a single plane and symmetrical from side to side. They come in various forms, including evolute shells where all whorls are exposed, and strongly involute shells with only the outer whorl visible. Shells may be heavily ribbed, with some featuring nodes and spines, while others are completely smooth. Some shells have broad, rounded venters (the outer rim), while others have a sharp, keel-like venter. Sutures are generally ammonitic, characterized by complex saddle and lobe patterns. However, in some derived forms, the suture pattern becomes simplified, appearing ceratitic or even goniatitic. The Ammonitina are ... [...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. Ammonites (Apoderoceras) were predatory mollusks that resembled a squid with a shell. These cephalopods had eyes, tentacles, and spiral shells. They are more closely related to a living octopus, though the shells resemble that of a nautilus. True ammonites appeared in the fossil record about 240 million years ago. The last lineages disappeared 65 million years ago at the end of the Cretaceous.https://www.fossilera.com/fossils/huge-13-spiny-jurassic-ammonite-apoderoceras-fossil-england 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 Trias ... [...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 on Invertebrate Paleontology, 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 on Invertebrate Paleontology, 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 (ammonite), Pleuroceras''. ''Amaltheus'' is oxyconic, keeled, strigated, and ribbed on the outer flanks. ''Amauroceras'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
