Over time surface began to be given greater consideration and by later Classical times culminated in works like "Marathon Boy" thought by some to be the work of Praxiteles the most famous of later classical Greek sculptors. These three examples of Greek sculpture share some fundamental things. Each is a treatment of a male nude. Each could be said to combine naturalistic observation of living models with abstract canons of proportion.
If works like these could be said to be one development from the kouros figure perhaps the sculptural group treating a legendary event is another......See Laocoon and his Sons-A Further Analysis (this blog)