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Cymbitidae
Cymbitidae is family of ammonite that lived during Sinemurian and Pliensbachian stages of Lower Jurassic. They have probably evolved from Arietitidae Arietitidae is a family of true ammonites that make up part of the superfamily Psiloceratoidea, named after the type genus ''Arietites''. They comprise medium-size to large or gigantic genera which in general are strongly ribbed, tuberculate in s .... Description Ammonites belonging to this family had shells with sphaeroconic involute inner whorls that later during ontogeny become evolute and last whorl is highly eccentric. They were small and mostly less than 2 cm in diameter. Venter is smooth, fastigate or rounded. There was constriction on aperture. Ornamentation was weak, as shell was smooth or plicate and only rarely there were lateral tubercules. Genera Cymbitidae is probably monogeneric family. It is named after genus '' Cymbites'' Neumayr, 1878. One more genus has been added there and it is '' Hyerifalchia'' Fucini, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Psiloceratoidea
Psiloceratoidea is a superfamily of Early Jurassic ammonoid cephalopods proposed by Hyatt in 1867, assigned to the order Ammonitida. They were very successful during Hettangian and Sinemurian. Last of them, family Cymbitidae and genera ''Hypoxynoticeras'' and ''Radstockiceras'' survived into Early Pliensbachian. Psiloceratoidea is probably derived from the family Ussuritidae, which were Triassic members of Phylloceratoidea. Similar to their ancestors, Psiloceratidae kept smooth, rounded venter for whole of their life. Schlotheimiidae were different, as they had ventral chevrons. Rest of the families had angular venter, or keel for at least part of their ontogeny. Most of the members of this superfamily had only simple ribs, but few of them have evolved also secondary ribbing. While some members are involute and some Oxynoticeratidae were oxycone, most of the species were evolute. Families *Psiloceratidae - Evolute shells with simple, or missing ribs. An venter, there is no o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonites
Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) than they are to shelled nautiloids such as the living ''Nautilus'' species. The earliest ammonites appeared during the Devonian, with the last species vanishing during the Cretaceous–Paleogene extinction event. Ammonites are excellent index fossils, and linking the rock layer in which a particular species or genus is found to specific geologic time periods is often possible. Their fossil shells usually take the form of planispirals, although some helically spiraled and nonspiraled forms (known as heteromorphs) have been found. The name "ammonite", from which the scientific term is derived, was inspired by the spiral shape of their fossilized shells, which somewhat resemble tightly coiled rams' horns. Pliny the Elder ( 79 AD near Pomp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sinemurian
In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic Epoch or Series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago). The Sinemurian is preceded by the Hettangian and is followed by the Pliensbachian. In Europe the Sinemurian age, together with the Hettangian age, saw the deposition of the lower Lias, in Great Britain known as the Blue Lias. Stratigraphic definitions The Sinemurian Stage was defined and introduced into scientific literature by French palaeontologist Alcide d'Orbigny in 1842. It takes its name from the French town of Semur-en-Auxois, near Dijon. The calcareous soil formed from the Jurassic limestone of the region is in part responsible for the character of the classic Sancerre wines. The base of the Sinemurian Stage is at the first appearance of the ammonite genera ''Vermiceras'' and '' Metophioceras'' in the stratigraphic record. A global reference profile ( GSSP or golden spike) for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pliensbachian
The Pliensbachian is an age of the geologic timescale and stage in the stratigraphic column. It is part of the Early or Lower Jurassic Epoch or Series and spans the time between 190.8 ± 1.5 Ma and 182.7 ± 1.5 Ma (million years ago). The Pliensbachian is preceded by the Sinemurian and followed by the Toarcian. The Pliensbachian ended with the extinction event called the Toarcian turnover. During the Pliensbachian, the middle part of the Lias was deposited in Europe. The Pliensbachian is roughly coeval with the Charmouthian regional stage of North America. Stratigraphic definitions The Pliensbachian takes its name from the hamlet of Pliensbach in the community of Zell unter Aichelberg in the Swabian Alb, some 30 km east of Stuttgart in Germany. The name was introduced into scientific literature by German palaeontologist Albert Oppel in 1858. The base of the Pliensbachian is at the first appearances of the ammonite species '' Bifericeras donovani'' and genera ''Apoderocer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lower Jurassic
The Early Jurassic Epoch (in chronostratigraphy corresponding to the Lower Jurassic Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-Jurassic extinction event, 201.3 Ma (million years ago), and ends at the start of the Middle Jurassic 174.1 Ma. Certain rocks of marine origin of this age in Europe are called "Lias" and that name was used for the period, as well, in 19th-century geology. In southern Germany rocks of this age are called Black Jurassic. Origin of the name Lias There are two possible origins for the name Lias: the first reason is it was taken by a geologist from an English quarryman's dialect pronunciation of the word "layers"; secondly, sloops from north Cornish ports such as Bude would sail across the Bristol Channel to the Vale of Glamorgan to load up with rock from coastal limestone quarries (lias limestone from South Wales was used throughout North Devon/North Cornwall as it con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arietitidae
Arietitidae is a family of true ammonites that make up part of the superfamily Psiloceratoidea, named after the type genus ''Arietites''. They comprise medium-size to large or gigantic genera which in general are strongly ribbed, tuberculate in some, with keeled or grooved and keeled venters, and well differentiated ammonitic sutures. The aptycus is single valved with a shiny, concentrically striated surface. Arietitidae dominated Lower Jurassic, Sinemurian ammonites, worldwide, extending into the lower Pliensbachian. The Arietitidae may have their origin in the Schlotheimiidae if not directly from the Psiloceratidae, and is the probably source for the Oxynoticeratidae Oxynoticeratidae is a family of true ammonites (order Ammonitida) included in the superfamily Psiloceratoidea. Oxynoticeratids have a broad, worldwide distribution but a narrow stratigraphic one, being known only from the Upper Sinemurian and .... References * * Donvan, D.T. and Callomon, J.H. 1981, Class ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonitida Families
Ammonitida is an order of Ammonoidea, 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sinemurian First Appearances
In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic Epoch or Series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago). The Sinemurian is preceded by the Hettangian and is followed by the Pliensbachian. In Europe the Sinemurian age, together with the Hettangian age, saw the deposition of the lower Lias, in Great Britain known as the Blue Lias. Stratigraphic definitions The Sinemurian Stage was defined and introduced into scientific literature by French palaeontologist Alcide d'Orbigny in 1842. It takes its name from the French town of Semur-en-Auxois, near Dijon. The calcareous soil formed from the Jurassic limestone of the region is in part responsible for the character of the classic Sancerre wines. The base of the Sinemurian Stage is at the first appearance of the ammonite genera ''Vermiceras'' and '' Metophioceras'' in the stratigraphic record. A global reference profile ( GSSP or golden spike) for t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
