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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 difference between modern coleoids and nautiluses is great today, but the fossil neocephalopods show that many of the differences accumulated piecemeal. These fossil forms include belemnoids, ammonoids, the bactritids, and some orthocerid-type nautiloids. ==Taxonomic history== The name Neocephalopoda was first published (in Lehmann & Hillmer, 1980) as an Infraclass, which (in a reversal of the usual Linnean hierarchy) included the Subclasses Bactritoidea, Ammonoidea, and Coleoidea. Neocephalopoda was a new name for a group that had been recognized previously and called Angusteradulata (Lehmann, 1967), based on a discovery of an ammonoid radula similar to modern coleoids. It was contrasted with the Lateradulata, which included the nautilus and most fossil nautiloids. These names were applied by later workers running cladistic analyses on the cephalopods. Berthold & Engeser (1987) adopted the name Angusteradulata for the clade comprising ammonoids and coleoids. Later, Engeser (1996) applied it to the total-group coleoids as described above. Thus he included not only the coleoids, ammonoids, and bactritids, but also some orthocerid families: Michelinoceratidae, Sphaerorthoceratidae, Arionoceratidae, "and probably other groups as well." Although the name Angusteradulata appeared earlier than Neocephalopoda, both names were coined by Lehmann, who preferred the latter. Engeser and Lehmann later both agreed that Neocephalopoda was a more suitable name than Angusteraduata. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Neocephalopoda」の詳細全文を読む スポンサード リンク
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