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Teleostomi
Teleostomi is a clade of jawed vertebrates that includes the tetrapods, bony fish, and the wholly extinct acanthodian fish. Key characters of this group include an operculum and a single pair of respiratory openings, features which were lost or modified in some later representatives. The teleostomes include all jawed vertebrates except the chondrichthyans and the extinct class placodermi.
The clade Teleostomi should not be confused with the similar-sounding fish clade Teleostei.
==Origins==
The origins of the teleostomes are obscure. They are traditionally assumed to be descendents of the Acanthodians ("spiny sharks") from the Late Ordovician Period; however, more recent discoveries show that the "spiny sharks" are actually a paraphyletic assemblage leading to Chondrichthyes, and that placoderms like ''Entelognathus'' are more closely related to true bony fish.〔(A Silurian placoderm with osteichthyan-like marginal jaw bones )〕 Living teleostomes constitute the clade Euteleostomi, which includes all osteichthyans and tetrapods. Even after the acanthodians perished at the end of the Permian, their euteleostome relatives flourished such that today they comprise 99% of living vertebrate species.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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