Ammonoids are extinct spiral shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living coleoids than they are to shelled nautiloids. The earliest ammonoids appeared during the Devonian, with the last species vanishing during or soon after the Cretaceous–Paleogene extinction event. 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.
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 group of marine cephalopods (Mollusca) which originated in the Late Cambrian and are represented today by the living Nautilus and Allonautilus. Fossil nautiloids are diverse and species rich, with over 2,500 recorded species. They flourished during the early Paleozoic era, when they constituted the main predatory animals. Early in their evolution, nautiloids developed an extraordinary diversity of shell shapes, including coiled morphologies and giant straight-shelled forms (orthocones). No orthoconic and only a handful of coiled species, the nautiluses, survive to the present day.
Baculites is an extinct genus of heteromorph ammonite cephalopods with almost straight shells. 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.
Sculpture is a feature of many of the shells of mollusks. It is three-dimensional ornamentation on the outer surface of the shell, as distinct from either the basic shape of the shell itself or the pattern of colouration, if any. Sculpture is a feature found in the shells of gastropods, bivalves, and scaphopods. The word "sculpture" is also applied to surface features of the aptychus of ammonites, and to the outer surface of some calcareous opercula of marine gastropods such as some species in the family Trochidae.
In the geologic time scale, the Changhsingian or Changxingian is the latest age or uppermost stage of the Permian. It is also the upper or latest of two subdivisions of the Lopingian Epoch or Series. The Changhsingian lasted from 254.14 to 251.9 Ma ago. It is preceded by the Wuchiapingian age/stage and is followed by the Induan age/stage.
Stenopterygius is an extinct genus of thunnosaur ichthyosaur known from Europe.
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.
The Early Devonian is the first of three epochs comprising the Devonian period, corresponding to the Lower Devonian series. It lasted from 419.2 ± 3.2 to 393.3 ± 1.2 and began with the Lochkovian Stage 419.2 ± 3.2 to 410.8 ± 1.2, which was followed by the Pragian from 410.8 ± 3.2 to 407.6 ± 1.2 and then by the Emsian, which lasted until the Middle Devonian began, 393.3± 1.2 million years ago. During this time, the first ammonoids appeared, descending from bactritoid nautiloids. Ammonoids during this time period were simple and differed little from their nautiloid counterparts. These ammonoids belong to the order Agoniatitida, which in later epochs evolved to new ammonoid orders, for example Goniatitida and Clymeniida. This class of cephalopod molluscs would dominate the marine fauna until the beginning of the Mesozoic Era.
Xenoceltites is an extinct genus of ceratite ammonoid found worldwide in the Lower Triassic.
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 Paragastrioceratidae family. The only species is Anatsabites multiliratus, formerly placed into genus Paraceltites. Its fossils were found in Wordian (Permian) of Texas.
Parastrenoceras is an extinct genus from the ammonoid cephalopod order Ammonitida, included in the family Spiroceratidae that lived during the Bajocian stage of the Middle Jurassic.
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 most common in Europe, North Africa, and South China but are known from North America and Australia as well.
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.
Meekoceras is an extinct genus of ceratitid ammonites with a discoidal shell that lived during the Early Triassic Epoch.
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.
This list of fossil molluscs described in 2021 is a list of new taxa of fossil molluscs that were described during the year 2021, as well as other significant discoveries and events related to molluscan paleontology that occurred in 2021.
