. "Asteroceras"@en . "The Ammonoidea constitute a subclass of extinct cephalopods found in marine sediments from the Early Devonian through the Cretaceous. Baring an external shell, ammonoids superficially resemble nautiloids, such as the modern Nautilus . however, based on similarity of the radulas, they are more closely related to modern coleoids , squid, octopus, and cuttlefish. Ammonoids are commonly referred to in the vernacular as Ammonites, although the term is often reserved for members of the order Ammonitida. For derivation and history of the term see Ammonite"@en . . . "Ammonoidea"@en . . . . "Orders and Suborders"@en . "(Karl Alfred von Zittel, 1884 )"@en . . . . "Ammonioidea"@en . . . . . . . "Ammonoidea"@en . . "Class"@en . . . . . . . . . "The Ammonoidea constitute a subclass of extinct cephalopods found in marine sediments from the Early Devonian through the Cretaceous. Baring an external shell, ammonoids superficially resemble nautiloids, such as the modern Nautilus . however, based on similarity of the radulas, they are more closely related to modern coleoids , squid, octopus, and cuttlefish. Ammonoids are commonly referred to in the vernacular as Ammonites, although the term is often reserved for members of the order Ammonitida. For derivation and history of the term see Ammonite Ammonoid shells usually take the form of planispirals, although there were some helically-spiraled and non-spiraled forms (known as \"heteromorphs\"). Often with short stratigraphic ranges, they make excellent index fossils, making it possible to link the rock layer in which they are found to specific stage or substage within a given geologic period."@en . . . . . . "Order Agoniatitida\n* Anarcestina\n* Pharciceratina\n* Prolobinina\nOrder Ammonitida\n* Ammonitina\n* Phylloceratina\n* Lytoceratina\nOrder Ceratitida\n* Ceratitina\n* Otoceratina \n* Noritacina\n* Clydonitina\nOrder Clymeniida\n* Clymeniina\n* Gonioclymeniina\n* Cyrtoclymeniina\nOrder Goniatitida\n* Goniatitina\n* Tornoceratina\nOrder Prolecanitida\n* Prolecanitina\n* Medlicottiana"@en . "Subclass"@en . . . . . . . . .