Teleostomi is a clade of jawed vertebrates that ines the tetrapods, bony fish, and the wholly extinct acanthodian fish. Key chacters of this group include an operculum and a single pair of respiratory openings, features which were lost or modified in some later representatives. eleostomes include all jawed vertebrates except the chondrichthyans and t
The clade Teleostomi should not be confused with the similar-souning fish clade Teleosei.
Taxonomy and phylogenyEdit
Subphylum Vertebrata ├─(unranked) Gnathostomatomorpha └─Infraphylum Gnathostomata ├─Class Placodermi - extinct (armored gnathostomes) └Microphylum Eugnathostomata (true jawed vertebrates) ├─Class Chondrichthyes (cartilaginous fish) └─(unranked) Teleostomi (Acanthodii & Osteichthyes) ├─Class Acanthodii - extinct ("spiny sharks") ├Superclass Osteichthyes (bony fish) ├ ├─Class Actinopterygii (ray-finned fish) ├ └─Class Sarcopterygii (lobe-finned fish) └Superclass Tetrapoda ├─Class Amphibia (amphibians) └(unranked) Amniote (amniotic egg) ├─Class Sauropsida (reptiles or sauropsids) ├ └─Class Aves (birds) └─Class Synapsid └─Class Mammalia (mammals) Note: lines show evolutionary relationships.
The origins of the teleostomes are obscure, but their first known fossils are Acanthodians ("spiny sharks") from the Late Ordovician Period. 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.
Teleostomes have two major adaptations that relate to aquatic respiration. First, the early teleostomes probably had some type of operculum, however, it was not the one-piece affair of living fish. The development of a single respiratory opening seems to have been an important step. The second adaptation, the teleostomes also developed a gas bladder and the ability to use some atmospheric oxygen, if primarily for buoyancy, very early on. The primary function of the bladder is keeping the fish at neutral buoyancy. Later these swim bladders will evolve and modify into lungs, as in tetrapods.Template:Fact
Acanthodians share with Actinopterygii the characteristic of three otoliths, the sagitta in the sacculus, the asteriscus in the lagena, and the lapillus in the utriculus. In dipnoans there are only two otoliths and in Latimeria there is only one.