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, with the last species vanishing during or soon after the Cretaceous–Paleogene extinction event.
Stephanoceras is an extinct genus of Stephanoceratoid ammonite which lived during the Bajocian. It is the type genus of the family Stephanoceratidae.
Australiceras is an extinct ammonite genus from the upper part of the Early Cretaceous, Aptian stage, included in the family Ancyloceratidae.
Aegocrioceras is an extinct ammonite genus of cephalopod from the Lower Cretaceous included in the Ammonitida. It is known from northern Europe.
Audaxlytoceras is an extinct genus of lytoceratid ammonites.
Arcticoceras is an extinct ammonoid cephalopod genus from the late Middle Jurassic belonging to the ammonite family Cardioceratidae, more commonly found to high northern latitudes.
Ceratitida is an order that contains almost all ammonoid cephalopod genera from the Triassic as well as ancestral forms from the Upper Permian, the exception being the phylloceratids which gave rise to the great diversity of post-Triassic ammonites.
Parapuzosia is an extinct genus of desmoceratid ammonites from the Cenomanian to the Campanian of Africa, Europe, and North America. They are typically very large ammonites, reaching diameters of 60 cm (2.0 ft) or more, with the largest species measuring upwards of more than 2.5 m (8.2 ft). It possesses a moderately involute shell with flat or slightly rounded sides. Distinct primary and secondary ribbing can be observed in the inner whorls.
Euaptetoceras is an evolute hildoceratoid ammonite from the lower Middle Jurassic, included in the family Hammatoceratidae and the subfamility Hammatoceratinae. The genus may be a junior synonym for Eudmetoceras of Buckman, 1920.
Durotrigensia is a genus of ammonites (Ammonitida) in the perisphinctoid family Parkinsoniidae.
Otoites is the type genus of the ammonite family Otoitidae that live during the Middle Jurassic.
Oecoptychius is an extinct genus of fossil ammonite cephalopods. The species lived during the Middle Jurassic.
Placenticeras is a genus of ammonites from the Late Cretaceous. Its fossils have been found in Asia, Europe, North and South America.
Exiteloceras is an ammonite genus from the Late Cretaceous.
Peltoceras is an extinct ammonite genus from the aspidoceratid subfamily Peltoceratinae that lived during the later part of the Middle Jurassic.
Eoderoceras is an evolute, round whorled ammonite from the Lower Jurassic with an outer row of distinct spines, and in some, an inner row of tubercles, on either side; ribs only on the inner whorls.
Harpoceras is an extinct genus of ammonite belonging to the family Hildoceratidae. These cephalopods existed in the Jurassic period, during the Toarcian age from the Falciferum zone to the Commune subzone of the Bifrons zone. They were fast-moving nektonic carnivores.
Holcodiscus is an extinct ammonite genus placed in the family Holcodiscidae. Species in this genus were fast-moving nektonic carnivores. The type species of the genus is Ammonites caillaudianus.
Ochetoceras is a genus of ammonites, belonging to the Oppeliidae, that lived during the Late Jurassic from the early Oxfordian to the early Tithonian, and type for the subfamily Ochetoceratinae.
Porpoceras is genus of ammonite that lived during the early and middle Toarcian stage of early Jurassic. Members of this genus existed from uppermost part of the Harpoceras serpentinum zone to the Haugia variabilis zone. Their fossils were found in Europe, Asia, North America and South America.
