Members of class Osteichthyes differ from those of both Agnatha and Chondrichthyes in that Osteichthyans have what?

Members of class Osteichthyes, commonly known as bony fish, are characterized by possessing a bony skeleton, which is a defining feature that sets them apart from both Agnatha (jawless fish like lampreys and hagfish) and Chondrichthyes (cartilaginous fish like sharks and rays). The bony skeleton in Osteichthyans provides structural support and allows for a wider range of movement compared to the cartilaginous structure seen in Chondrichthyes.

Furthermore, the evolution of a bony skeleton allowed Osteichthyes to develop features such as swim bladders for buoyancy and more complex gill structures, which facilitate improved respiration and the ability to thrive in various aquatic environments. This contrast is essential in understanding the diversity and evolutionary adaptations of fish within vertebrate lineages. The other characteristics mentioned, such as a true jaw and gills, are present in both Chondrichthyes and Osteichthyes, while amniotic eggs are exclusive to reptiles and mammals, marking a different evolutionary path.