The key difference between Sarcopterygii and Actinopterygii is that sarcopterygii is a class of bony fish, consisting of lobed fish that have fleshy, lobed and paired fins. Meanwhile, actinopterygii is a class of bony fish, consisting of ray-finned fish that have fins supported by horny spines.
Fish that belong to the group osteichthyan are vertebrates. Their fins and the body structure may vary depending on the group. Sarcopterygii and actinopterygii are two classes of osteichthyans. Sarcopterygii fish are lobed finned fish while actinopterygii fish are ray-finned fish. Most species belonging into sarcopterygii are extinct in comparison to species belonging into actinopterygii.
