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 appear during the Devonian, and the last species vanished in the Cretaceous–Paleogene extinction event.
Goniatids, informally goniatites, are ammonoid cephalopods that form the order Goniatitida, derived from the more primitive Agoniatitida during the Middle Devonian some 390 million years ago. Goniatites (goniatitids) survived the Late Devonian extinction to flourish during the Carboniferous and Permian only to become extinct at the end of the Permian some 139 million years later.
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.
Septa are thin walls or partitions between the internal chambers (camerae) of the shell of a cephalopod, namely nautiloids or ammonoids.
In the geologic timescale, the Callovian is an age and stage in the Middle Jurassic, lasting between 166.1 ± 4.0 Ma and 163.5 ± 4.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the Oxfordian.
Xenodiscus is an extinct ammonoid cephalopod genus and one of the earliest ceratites, found in the Upper Permian of northern India and Timor. Xenodiscus is included in the family Xenodiscidae which is part of the ceratite superfamily Xenodiscaceae
Alaoceras is an ammonoid cephalopod from the upper Paleozoic included in the goniatitid family Cravenoceratidae, named by Ruzhentsev & Bogoslovskaya in 1971.
Arctoceras is a genus of ceratitid ammonoids from the Lower Triassic with a moderately narrow discoidal shell and ceratitic suture.
Dombarites is a genus belonging to the goniatitid family Agathiceratidae; extinct ammonoids which are shelled cephalopods more closely related to squid, octopus and other coleoids than to the superficially similar Nautilus
Dombarigloria is a genus belonging to the goniatitid family Cravenoceratidae; extinct ammonoids which are shelled cephalopods more closely related to squid, octopus and other coleoids than to the superficially similar Nautilus
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.
Goniatitina is one of two suborders included in the order Goniatitida; extinct Paleozoic ammonoid cephalopods only distantly related to the Nautiloidea.
Pseudohaloritidae is the larger of two families that form the goniatitid superfamily Pseudohaloritoidea, the other being the monogenerc Maximitidae. They are part of the vast array of shelled cephalopods known as ammonoids that are more closely related to squids, belemnites, octopuses, and cuttlefish, than to the superficially similar Nautilus.
Gastrioceratoidea is one of seventeen superfamilies in the suborder Goniatitina, ammonoid cephalopods from the Late Paleozoic.
Thalassoceratidae a family of late Paleozoic ammonites included in the goniatitid superfamily Thalassoceratoidea along with the Bisatoceratidae. Some eight genera are included, although the specific number and exactly which depends on the particular classification.
The Cravenoceratidae is one of six families included in the ammonoid superfamily Neoglyphioceratoidea, which lived during the latter part of the Paleozoic era.
Prolecanitida is an order of extinct ammonoid cephalopods with discoidal to thinly lenticular shells with goniatitic or ceratitic sutures and which retained the simple retrochoanitic siphuncle with backward extending septal necks. As typical for ammonoids the siphuncle is along the ventral margin. Prolecanitids form a relatively small and stable order within the Ammonoidea with 43 named genera and about 1250 species, but with a long-ranging lineage of about 108 m.y. stretching from the Lower Carboniferous to the Triassic. Although not as diverse as their goniatitid contemporaries, the Prolecanatida provided the stock from which all later Mesozoic ammonoids were derived.
Flemingites is a genus of evolute ammonoids from the Lower Triassic with spiral ridges on the shell.
Sturia is a genus of ceratitid ammonoids from the Lower Triassic with an ammonitic suture.
Choristocerataceae is a superfamily of Late Triassic ceratitidan ammonites. They can be characterized by their simple, four-lobed suture lines and unusual heteromorph shell shapes, which can resemble straight rods or twisting cones rather than the flat coils typical of other ammonites. The shells are usually small and ornamented with prominent ribbing.
