classification of living species造句

What the paleontologists mean ( and classification of extinct species is quite different from classification of living species ) is that ancestors of primates at the point in time in which primates began to separate from rodents ( at which time, yes, they all pretty much looked like rats ) were more like Purgatorius than they were like the other protorodents running around at the time.
It's difficult to find classification of living species in a sentence. 用classification of living species造句挺难的