Page "Sarcopterygii" Paragraph 4

Sarcopterygians and their relatives the actinopterygians (" ray-finned fish ") comprise the superclass Osteichthyes, the " bony fish ", characterized by their bony skeleton rather than cartilage.

There are otherwise vast differences in fin, respiratory, and circulatory structures between the Sarcopterygii and the Actinopterygii.

The first sarcopterygians, found in the uppermost Silurian ( ca 418 Ma ), closely resembled the Acanthodians ( the " spiny fish ", a taxon that went extinct at the end of the Paleozoic ).

In the early – middle Devonian ( 416-385 Ma ), while the predatory placoderms dominated the seas, some sarcopterygians came into freshwater habitats.