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Osteichthyes (IPA: /ˌɒstiːˈɪkθiːz/), also called bony fish, are a taxonomic Class of fish that includes the ray-finned fish (Actinopterygii) and lobe finned fish (Sarcopterygii). The split between these two classes occurred around 440 mya.[1] In most classification systems[2] the Osteichthyes are paraphyletic with land vertebrates. That means that the nearest common ancestor of all Osteichthyes includes tetrapods amongst its descendants. Actinopterygii (ray-finned fish) are monophyletic, but the inclusion of Sarcopterygii in Osteichthyes causes Osteichthyes to be paraphyletic. Most bony-fish belong to the Actinopterygii; there are only eight living species of lobe finned fish (Sarcopterygii) including the lungfish and coelacanths.(Some species of lobe-finned fish have jointed bones.) They are traditionally treated as a class of vertebrates, with subclasses Actinopterygii and Sarcopterygii, but some newer schemes divide them into several separate classes. The vast majority of fish are osteichthyes. Osteichthyes are the most various group of vertebrates, consisting of over 29,000 species, making them the largest class of vertebrates in existence today.