| Cheltonia Temporal range: | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Subclass: | † Ammonoidea |
| Order: | † Ammonitida |
| Family: | † Oxynoticeratidae |
| Genus: | † Cheltonia Buckman, 1904 |
| Type species | |
| Ammonites accipitris Buckman, 1844 | |
| Species | |
| |
Cheltonia is an extinct genus of ammonite from the Upper Sinemurian substage of Lower Jurassic of Europe, Africa, [2] and America.[ citation needed ] It is probably a microconch of genus Oxynoticeras . [1]
Ammonites belonging to this genus had small platyconic shell, on which the last whorl has been eccentrically coiled. Ventral rostrum could be preceded by 3 to 5 crawlings. Umbilicus took about 30—40% of diameter. Ribs were falcoid and weak. Suture has been the same as in the case of young Oxynoticeras. [1]
Ammonoids are extinct spiral shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living coleoids than they are to shelled nautiloids. The earliest ammonoids appeared during the Devonian, with the last species vanishing during or soon after the Cretaceous–Paleogene extinction event. They are often called ammonites, which is most frequently used for members of the order Ammonitida, the only remaining group of ammonoids from the Jurassic up until their extinction.
Hamites is a genus of heteromorph ammonite that evolved late in the Aptian stage of the Early Cretaceous and lasted into the Cenomanian stage of the Late Cretaceous. The genus is almost certainly paraphyletic but remains in wide use as a "catch all" for heteromorph ammonites of the superfamily Turrilitoidea that do not neatly fit into the more derived groupings. In an attempt to identify clades within the genus, it has been divided up into a series of new genera or subgenera by different palaeontologists, including Eohamites, Hamitella, Helicohamites, Lytohamites, Planohamites, Psilohamites, and Sziveshamites.
Dactylioceras was a widespread genus of ammonites from the Lower Jurassic period, approximately 180 million years ago (mya).
The Ancyloceratina were a diverse suborder of ammonite most closely related to the ammonites of order Lytoceratina. They evolved during the Late Jurassic but were not very common until the Cretaceous period, when they rapidly diversified and became one of the most distinctive components of Cretaceous marine faunas. They have been recorded from every continent and many are used as zonal or index fossils. The most distinctive feature of the majority of the Ancyloceratina is the tendency for most of them to have shells that are not regular spirals like most other ammonites. These irregularly-coiled ammonites are called heteromorph ammonites, in contrast to regularly coiled ammonites, which are called homomorph ammonites.
The Hettangian is the earliest age and lowest stage of the Jurassic Period of the geologic timescale. It spans the time between 201.3 ± 0.2 Ma and 199.3 ± 0.3 Ma. The Hettangian follows the Rhaetian and is followed by the 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 199.5 ±0.3 Ma and 192.9 ±0.3 Ma. The Sinemurian is preceded by the Hettangian and is followed by the Pliensbachian.
Lusitanosaurus is a genus of reptile from the Sinemurian stage of Early Jurassic of Portugal, maybe from the Coimbra Formation. It was considered the second example of the Dinosaurian group Thyreophora from the Sinemurian of Europe and it the oldest known dinosaur from the Iberian Peninsula, but this affinity has been contested. It is based on a large left maxilla with teeth that was lost in the fire at Museu Nacional de História Natural e da Ciência, Lisbon, in 1978.
Acanthohoplites is an extinct genus of ammonites in the family Parahoplitidae that lived in the Aptian and Early Albian stages of the Early Cretaceous.
Oxynoticeras is an extinct genus of ammonite from the Early Jurassic of Europe and North America. This genus is characterized by its smooth shell, with almost invisible undulations on the flank, and a sharp keel.
Pachycormus is an extinct genus of pachycormiform ray-finned fish known from the Early Jurassic of Europe.
Sphenodiscus is an extinct genus of acanthoceratacean ammonite. The genus has been found from many continents and is thought to have had a large global distribution during the Maastrichtian stage of the Late Cretaceous. It was one of the last ammonoids to have evolved before the entire subclass became extinct during the Paleocene, which was directly after the Cretaceous–Paleogene extinction event.
Simosaurus is an extinct genus of marine reptile within the superorder Sauropterygia from the Middle Triassic of central Europe. Fossils have been found in deposits in France and Germany that are roughly 230 million years old. It is usually classified as a nothosaur, but has also been considered a pachypleurosaur or a more primitive form of sauropterygia.
Oxynoticeratidae is a family of true ammonites included in the superfamily Psiloceratoidea.
Macroscaphites is an extinct cephalopod genus included in the Ammonoidea that lived during the Barremian and Aptian stages of the Early Cretaceous. Its fossils have been found throughout most of Europe and North Africa.
Cephalopod egg fossils are the fossilized remains of eggs laid by cephalopods. The fossil record of cephalopod eggs is scant since their soft, gelatinous eggs decompose quickly and have little chance to fossilize. Eggs laid by ammonoids are the best known and only a few putative examples of these have been discovered. The best preserved of these were discovered in the Jurassic Kimmeridge Clay of England. Currently no belemnoid egg fossils have ever been discovered although this may be because scientists have not properly searched for them rather than an actual absence from the fossil record.
Eucalycoceras is an extinct genus of cephalopods belonging to the Ammonite subclass.
Radstockiceras is an extinct genus of lower Jurassic ammonite that lived from Oxynotum zone of upper Sinemurian to Raricostatum zone of lower Pliensbachian. Shells of these animals were oxycone and involute with umbilicus that took maximum of 12% of diameter in the case of outer whorls. On inner whorls, venter has been sharp, but then it became rounded. Faint ribs had falcoid shape, but sometimes, ribs could absent. Shells could have been large in their size. Suture has been very complex, similar to Oxynoticeras, but culmination at umbilical margin has been missing. Genus has been named after town of Radstock, in Somerset.
Paroxynoticeras is an extinct genus of lower Jurassic ammonite that lived during upper Sinemurian. Animals belonging to this genus had platyconic shells with compressed whorl section and could grow to large sizes. In the case of young specimens, umbilicum is small, but it increases in bigger specimens.. Last whorl is excentric, which can occur also in relative species, Paracymbites. While on the outer whorls, venter is always rounded, on inner whorls it can be both rounded or sharp. Ornamentation on inner whorls and suture is similar to Oxynoticeras, but in bigger specimens, ribs became straight, simple and blunt. In these bigger specimens, midlateral tubercules might be present.
Reynesocoeloceras is genus of ammonite that lived during the lower Pliensbachian stage of early Jurassic, ammonite zones Ibex—Davoei.
Leyvachelys is an extinct genus of turtles in the family Sandownidae from the Early Cretaceous of the present-day Altiplano Cundiboyacense, Eastern Ranges, Colombian Andes. The genus is known only from its type species, Leyvachelys cipadi, described in 2015 by Colombian paleontologist Edwin Cadena. Fossils of Leyvachelys have been found in the fossiliferous Paja Formation, close to Villa de Leyva, Boyacá, after which the genus is named. The holotype specimen is the oldest and most complete sandownid turtle found to date.
 | This Ammonitina-related article is a stub. You can help Wikipedia by expanding it. |