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The fossil record is incomplete enough that if you’re in a new area or a new time, there’s a fair chance that the dinosaurs there are going to be distinct, Steven Jasinski said. For instance, scientists might discover a toe from a brand new species, but such subtle differences may be unrecognizable or impossible to prove. [ T ] hings that we call separate species today would be very, very hard to tell apart based on their skeleton( crow versus raven, for example).