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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 ...
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.
This list of ammonites is a comprehensive listing of genera that are included in the subclass †Ammonoidea, excluding purely vernacular terms. The list includes genera that are commonly accepted as valid, as well as those that may be invalid or doubtful ( nomina dubia ), or were not formally published ( nomina nuda ), as well as junior ...
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.
Acanthoceras fossils have been found in Australia, Brazil, Bulgaria, Colombia (Hondita Formation, Prado, Tolima), [2] Denmark, Egypt, Marocco, France, Germany, India ...
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.
Parkinsonia is a genus of ammonites belonging to the family Parkinsoniidae. [ 2 ] These fast-moving nektonic carnivores lived from the Bajocian age to the Bathonian age of the Middle Jurassic .
Asteroceras stellare, the true star ammonite, is an extinct species of cephalopod belonging to the Ammonite subclass and to the family Arietitidae. [ 1 ] These fast-moving nektonic carnivores lived during the lower Jurassic period, around 196.5 to 189.6 million years ago.