Euteleostomes originally all had an endochondral bone, fins with lepidotrichs (fin rays), jaws lined by maxillary, premaxillary, and dentary bones composed of dermal bone, and lungs. Many of these characters have since been lost by descendant groups, however, such as lepidotrichs lost in tetrapods, and bone lost among the chondrostean fishes. Lungs have been retained in dipnoi (lungfish), and many tetrapods (birds, mammals, reptiles, and some amphibians). In many ray-finned fishes, lungs have evolved into swim bladders for regulating buoyancy, while in others they continue to be used as respiratory gas bladders.[5][6][7]
Euteleostomi vs. Osteichthyes
In ichthyology the difference between Euteleostomi and Osteichthyes is that the former presents a cladistic view, i.e. that the terrestrial tetrapods evolved from lobe-finned fish (Sarcopterygii). Until recently, the view of most ichthyologists has been that Osteichthyes were paraphyletic and include only bony fishes.[8] However, since 2013 widely cited ichthyology papers have been published with phylogenetic trees that treat the Osteichthyes as a clade including tetrapods, making the terms Euteleostomi and Osteichthyes synonymous.[8][9][10][11]
^Betancur-R, R., Wiley, E.O., Arratia, G., Acero, A., Bailly, N., Miya, M., Lecointre, G. and Orti, G. (2017) "Phylogenetic classification of bony fishes". BMC evolutionary biology, 17(1): 162. doi:10.1186/s12862-017-0958-3.
^Hughes, L.C., Ortí, G., Huang, Y., Sun, Y., Baldwin, C.C., Thompson, A.W., Arcila, D., Betancur-R, R., Li, C., Becker, L. and Bellora, N. (2018) "Comprehensive phylogeny of ray-finned fishes (Actinopterygii) based on transcriptomic and genomic data". Proceedings of the National Academy of Sciences, 115(24): 6249–6254. doi:10.1073/pnas.1719358115.