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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 vanished in the Cretaceous–Paleogene extinction event.
The Nautilida constitute a large and diverse order of generally coiled nautiloid cephalopods that began in the mid Paleozoic and continues to the present with a single family, the Nautilidae which includes two genera, Nautilus and Allonautilus, with six species. All told, between 22 and 34 families and 165 to 184 genera have been recognised, making this the largest order of the subclass Nautiloidea.
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.
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, was named by Lamarck in 1799.
Orthocerida is an order of extinct Orthoceratoid cephalopods also known as the Michelinocerida that lived from the Early Ordovician possibly to the Late Triassic. A fossil found in the Caucasus suggests they may even have survived until the Early Cretaceous. They were most common however from the Ordovician to the Devonian.
The Bactritida are a small order of more or less straight-shelled (orthoconic) cephalopods that first appeared during the Emsian stage of the Devonian period with questionable origins in Pragian stage before 409 million years ago, and persisted until Carnian pluvial event in the upper middle Carnian stage of the Triassic period. They are considered ancestors of the ammonoids, as well as of the coleoids.
Neocephalopods are a group of cephalopod mollusks that include the coleoids and all extinct species that are more closely related to extant coleoids than to the nautilus. In cladistic terms, it is the total group of Coleoidea. In contrast, the palcephalopoda are defined as the sister group to the neocephalopoda.
The Pragian is one of three faunal stages in the Early Devonian epoch. It lasted from 410.8 ± 2.8 million years ago to 407.6 ± 2.8 million years ago. It was preceded by the Lochkovian stage and followed by the Emsian stage. The most important Lagerstätte of the Pragian is Rhynie chert in Scotland. It is named after the city of Prague. The GSSP is located within the Praha Formation at Velká Chuchle, Prague.
Dimeroceratoidea, formerly Dimerocerataceae, is one of six superfamilies in the gonititid suborder Tornoceratina which lived During the Devonian. Five families are included, the Dimeroceratidae being the type family.
The Actinocerida are an order of generally straight, medium to large cephalopods that lived during the early and middle Paleozoic, distinguished by a siphuncle composed of expanded segments that extend into the adjacent chambers, in which deposits formed within contain a system of radial canals and a narrow space along the inner side of the connecting ring known as a paraspatium. Septal necks are generally short and cyrtochoanitic, some being recumbent, some hook shaped. Most grew to lengths of about 60 to 90 cm but some, like the Huroniidae of the Silurian grew significantly larger.
Agoniatitida, also known as the Anarcestida, is the ancestral order within the cephalopod subclass Ammonoidea originating from bactritoid nautiloids, that lived in what would become Africa, Asia, Australia, Europe, and North America during the Devonian from about the lower boundary of Zlichovian stage into Taghanic event during upper middle Givetian, existing for approximately 25 million years.
Jovellania is a genus of extinct prehistoric nautiloids from the order Oncocerida known from the Lower Devonian of Europe. 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.
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.
Ankyloceras is a genus of Early Devonian cephalopods included in the oncocerid family Karoceratidae. The type species, Ankyloceras nesnayamiense named by Zhuravleva, 1974, comes from Nova Zemlya in Russia. Other species have been found in Japan, Morocco, and Russia.
Pseudorthoceratidae is an extinct family of actively mobile aquatic carnivorous cephalopods belonging to the subclass Orthoceratoidea endemic to what would be North America, Asia, and Europe during the Silurian living from 460.5—251 Ma, existing for approximately 209.5 million years .
Parasphaerorthoceras is an extinct orthocerid genus, a nautiloid cephalopod, that lived in what would be Europe and north Africa during the Silurian from 422.9—418.1 mya, having existed for approximately 4.8 million years .
Orthoceratoidea is a subclass, formerly considered an infraclass or a superorder, that comprises Cephalopoda orders that have orthoconic to slightly cyrtoconic shells and central to subcentral siphuncles in which there may be internal deposits. Currently, Orthoceratoidea comprises the orders Dissidocerida, Ascocerida, Pseudorthocerida, Lituitida and Orthocerida.
The cephalopods have a long geological history, with the first nautiloids found in late Cambrian strata, and purported stem-group representatives present in the earliest Cambrian lagerstätten.
Conostichoceras is a genus of exogastric, breviconic oncocerids included in the family Nothoceratidae, known from the Middle Devonian of central Europe and Upper Devonian of Australia. It probably lived on and swum above the sea floor.
References
- ↑ Kröger, B. (2008). "Nautiloids before and during the origin of ammonoids in a Siluro-Devonian section of the Tafilalt, Anti-Atlas, Morocco". Special Papers in Palaeontology. Palaeontological Association, London. 79: 1–110. ISBN 978-1-4051-8770-1.
- ↑ Kröger, B; Mapes, R. H. (2007). "On the origin of bactritoids (Cephalopoda)". Paläontologische Zeitschrift. 81 (3): 316–327. doi:10.1007/BF02990181. S2CID 129091196.
- ↑ "Sphaerorthoceratidae - Age Range and Collections". The Paleobiology Database. Retrieved 18 July 2012.