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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. [2] 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 ...
Perisphinctes is an extinct genus of ammonite cephalopod. They lived during the Middle to Late Jurassic epochs and serve as an index fossil for that time period. [5] The species P. boweni was named after the English chemist and geologist E. J. Bowen (1898–1980). [6]
Parapuzosia seppenradensis is the largest known species of ammonite. [1] It lived during the Lower Campanian Epoch of the Late Cretaceous period, in marine environments in what is now Westphalia, Germany. A specimen, found in Seppenrade near Lüdinghausen, Germany in 1895 measures 1.8 m (5.9 ft) in diameter, although the living chamber is ...
Ammolite comes from the fossil shells of the Upper Cretaceous disk-shaped ammonites Placenticeras meeki and Placenticeras intercalare, and (to a lesser degree) the cylindrical baculite, Baculites compressus. Ammonites were cephalopods, that thrived in tropical seas until becoming extinct along with the dinosaurs at the end of the Mesozoic era.
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 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.
A fossil of Hoploscaphites, an ammonite believed to have survived the K-Pg extinction event well into the Paleocene. The term Paleocene ammonites describes families or genera of Ammonoidea that may have survived the Cretaceous–Paleogene extinction event, which occurred 66.043 million years ago.
Ammonitida or "True ammonites" are 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 .