What is Nautiloid?
{{Automatic taxobox | name = Nautiloids | fossil_range = {{fossil range|495|0}}[[Late Cambrian]] – Recent | image = Nautilus-JB-01.jpg | image_caption = ''[[Nautilus pompilius]]'' | taxon = Nautiloidea | authority = [[Louis Agassiz|Agassiz]], 1847 | subdivision_ranks = Orders | subdivision = '''Palcephalopoda'''<br> *†[[Plectronocerida]] *†[[Ellesmerocerida]] *†[[Actinocerida]] *†[[Endocerida]] *†[[Tarphycerida]] *†[[Oncocerida]] *†[[Discosorida]] *[[Nautilida]] '''[[Neocephalopoda]]''' (in part)<br> *†[[Bactritida]] }} '''Nautiloids''' are a large and varied group of [[ocean|marine]] [[cephalopod]]s ([[Mollusca]]) in the [[subclass]] Nautiloidea. They began in the later [[Cambrian]]. ''[[Nautilus]]'' is the only surviving [[genus]]. Nautiloids flourished during the early [[Palaeozoic]] [[era]], when they were the main predatory animals. They developed an extraordinary range of shell shapes and forms. Some 2,500 species of [[fossil]] nautiloids are known, though only a few species survive today.<ref name=bigbook>Teichert C. 1988. Main features of cephalopod evolution. In ''The Mollusca'' vol 12, ''Paleontology and neontology of Cephalopods''. eds M.R. Clarke & E.R. Trueman. Academic Press, Harcourt Brace Jovanovich.</ref> == Taxonomic relationships == Nautiloids are among the group of animals known as [[cephalopoda|cephalopods]]. The cephalopods are an advanced class of [[Mollusca|molluscs]]. The cephalopods also include [[Ammonite|ammonoids]], [[Belemnite]]s and modern [[coleoidea|coleoids]] such as [[octopus]] and [[squid]]. Traditionally, the most common classification of the cephalopods has been a three-fold division into the nautiloids, ammonoids, and coleoids. This article is about nautiloids in that broad sense, sometimes called Nautiloidea ''sensu lato''. [[Cladistics|Cladistically]] speaking, nautiloids are a [[paraphyletic]] group united by shared primitive ([[basal]]) features not found in [[derived]] cephalopods. In other words, they are a [[evolutionary grade]] that is thought to have given r