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 than they are to shelled nautiloids such as the living Nautilus species. The earliest ammonites appeared during the Devonian, and the last species either vanished in the Cretaceous–Paleogene extinction event, or shortly after, during the Danian epoch of the Paleocene.
Nautiloids are a large and diverse group of marine cephalopods (Mollusca) belonging to the subclass Nautiloidea that began in the Late Cambrian and are represented today by the living Nautilus and Allonautilus. Nautiloids flourished during the early Paleozoic era, where they constituted the main predatory animals, and developed an extraordinary diversity of shell shapes and forms. Some 2,500 species of fossil nautiloids are known, but only a handful of species survive to the present day.
Baculites is an extinct genus of cephalopods with a nearly straight shell, included in the heteromorph ammonites. The genus, which lived worldwide throughout most of the Late Cretaceous, and which briefly survived the K-Pg mass extinction event, was named by Lamarck in 1799.
Septa are thin walls or partitions between the internal chambers (camerae) of the shell of a cephalopod, namely nautiloids or ammonoids.
Stenopterygius is an extinct genus of thunnosaur ichthyosaur known from Europe. This genus of ichthyosaur grew to a maximum length of 4 meters.
The Emsian is one of three faunal stages in the Early Devonian Epoch. It lasted from 407.6 ± 2.6 million years ago to 393.3 ± 1.2 million years ago. It was preceded by the Pragian Stage and followed by the Eifelian Stage. It is named after the Ems river in Germany. The GSSP is located in the Zinzil'ban Gorge in the Kitab State Geological Reserve of Uzbekistan, 35 centimetres (14 in) above the contact with the Madmon Formation.
Anagaudryceras is an extinct genus of ammonite from the later Cretaceous belonging to the Ammonoidea family Gaudryceratidae. Anagaudryceras has a moderately involute shell with a deep umbilicus and strongly ribbed outer whorl. Ribs are thick and rounded and cross over the venter uninterrupted.
Anatsabites is a monospecific genus of ammonoid cephalopods belonging to the Atsabitidae family. Only species is Anatsabites multiliratus, formerly placed into genus Paraceltites. Its fossils were found in Wordian (Permian) of Texas.
Araxoceras is an extinct genus of ceratitid ammonites that lived in the Late Permian marine environments of Iran, South China and Japan. The various species had distinctive, angular-cornered shells.
Aristoceratoides is an extinct ammonoid genus belonging to the goniatitid family Thalassoceratidae that lived during the Middle Permian. Named by Ruzhentsev, 1960, the type species is "Thalassoceras" varicosum Gemmellaro, 1887.
Hoploscaphites is an extinct ammonite genus from the Upper Cretaceous and the Lower Paleocene, included in the family Scaphitidae.
Brevicoceras is an extinct nautiloid genus from the order Oncocerida with wide distribution in the Middle Devonian in Eastern North America, Russia and Morocco. Nautiloids form a broad group of shelled cephalopods that were once diverse and numerous but are now represented by only a handful of species in two genera.
Clymeniida is an order of ammonoid cephalopods from the Upper Devonian characterized by having an unusual dorsal siphuncle. They measured about 4 cm (1.6 in) in diameter and are restricted to Europe, North Africa, and possibly Australia.
Meyerasaurus is an extinct genus of rhomaleosaurid known from Holzmaden, Baden-Württemberg of southwestern Germany.
Shouchangoceras is a genus of goniatitid pseudohaloritid ammonoids and is the type genus for the pseudohaloritid subfamily Shouchangocerinae. The genus is characterized by a compressed shell as much as 5 cm in diameter, with a strongly constricted mature peristome that has shallow dorsolateral sinus, a moderately deep rounded ventral sinus, but without conspicuous lappets, and ornamented by moderately strong transverse ribs and numerous stronger longitudinal lirae, producing a weakly reticulate pattern. Lobes are attenuate. The siphuncle is within the dorsal septal flecture.
Paraceltites is a genus of ammonoid cephalopods in the ceratitid family Paraceltitidae, known from the Middle and Upper Permian of Sicily, the Alps, Crimea, Texas and Mexico. The shell of Paraceltities is evolute with whorls compressed, venter arched and smooth, sides bearing ribs that slant somewhat forward dorso-ventrally. The suture is simple and goniatitic.
Marmornectes is a genus of pliosaurid known from the Middle Jurassic of Bedfordshire, United Kingdom.
Saxoceras is a genus of very evolute schlotheimiid ammonoids from the Lower Jurassic.
Phyllopachyceras is an extinct genus of ammonoid cephalopods belonging to the family Phylloceratidae. These nektonic carnivores lived in the Cretaceous, from Hauterivian to Maastrichtian to age.
Quenstedtoceras is a genus of ammonoid cephalopods that lived during the latter part of the Jurassic period in what is now France, Poland, Germany, and the United Kingdom.
