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Idoceras
''Idoceras'' is a genus of perisphictacean ammonite, belonging to the Perisphinctidae subfamily Idoceratinae. The genus is known from the Upper Jurassic, with a widespread distribution. Shells of ''Idoceras'' are evolute, with a wide umbilicus; ribbing strong, bifurcate high on flanks. Suture simpler than in the similar ''Ataxioceras ''Ataxioceras'' is an extinct Ammonite cephalopod genus confined to the Upper Jurassic of Europe, included in the superfamily Perisphinctoidea. Previously ''Ataxioceras'' was assigned to the Perisphinctidae but has now been placed in the Ataxioc ...''. References * Jurassic ammonites Ammonitida genera Perisphinctidae Ammonites of Europe {{ammonitina-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perisphinctidae
Perisphinctidae is a family of Middle and Upper Jurassic discoidal ammonites in the order Ammonitida. They have a shell morphology that is mostly evolute, typically with biplicate, simple, or triplicate ribbing. Large forms have simple apertures and smooth body chambers while small forms have lappets and ribbed body chambers. The ammonites of PerisphinctidaeD.T Donovan, J.H. Callomon and M.K. Howarth, 1981, Classification of the Jurassic Ammonitia. The Ammonoidea, Systematics Association special volume no. 18. M.R. House and J.R. Senior, (eds). were derived from the ancestral Stephanoceratidae in the Middle Jurassic Bajocian: perisphinctid ammonites ranged from the Bajocan until the Tithonian at the end of the Jurassic. This family forms the root stock of the Perisphinctoidea which gave rise directly or indirectly to the other perisphinctoid families. The Treatise on Invertebrate Paleontology (Part L, 1957) includes the subfamilies Leptosphinctinae, Zigzagiceratinae, Pseu ... [...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] |
Ataxioceras
''Ataxioceras'' is an extinct Ammonite cephalopod genus confined to the Upper Jurassic of Europe, included in the superfamily Perisphinctoidea. Previously ''Ataxioceras'' was assigned to the Perisphinctidae but has now been placed in the Ataxioceratidae for which it is the type genus. These fast-moving nektonic carnivores lived during the Jurassic period, from 155.7 to 150.8 Ma. Description The shell is evolute, strongly ribbed and moderately umbilicate. Primary ribs, on the order of 32 -36 per whorl, are sharp and widely spaced, originate at the umbilical shoulder. Secondary ribs form about mid flank, generally by trifurcation, but sometimes quadrifurcation (splitting into threes or sometimes fours) of the primaries. The umbilicus is about 0.4 the shell diameter. Distribution Fossils of species within this genus have been found in the Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jurassic Ammonites
The Jurassic ( ) is a geologic period and 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 Jurassic constitutes the middle period of the Mesozoic Era and is named after the Jura Mountains, where limestone strata from the period were first identified. The start of the Jurassic was marked by the major Triassic–Jurassic extinction event, associated with the eruption of the Central Atlantic Magmatic Province. The beginning of the Toarcian Stage started around 183 million years ago and is marked by an extinction event associated with widespread oceanic anoxia, ocean acidification, and elevated temperatures likely caused by the eruption of the Karoo-Ferrar large igneous provinces. The end of the Jurassic, however, has no clear boundary with the Cretaceous and is the only boundary between geological periods to remain formally undefined. By the beginning of the Jurassic, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonitida Genera
Ammonitida is an order of ammonoid cephalopods that lived from the Jurassic through Paleocene time periods, commonly with intricate ammonitic sutures. Ammonitida is divided into four suborders, the Phylloceratina, Lytoceratina, Ancyloceratina, and Ammonitina. The Phylloceratina is the ancestral stock, derived from the Ceratitida near the end of the Triassic. The Phylloceratina gave rise to the Lytoceratina near the beginning of the Jurassic which in turn gave rise to the highly specialized Ancyloceratina near the end of the Jurassic. Both the Phylloceratina and Lytoceratina gave rise to various stocks combined in the Ammonitina. These four suborders are further divided into different stocks, comprising various families combined into superfamilies. Some like the Hildoceratoidea and Stephanoceratoidea are restricted to the Jurassic. Others like the Hoplitoidea and Acanthoceratoidea are known only from the Cretaceous. Still others like the Perisphinctoidea are found in both. R ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
