User blog comment:KrspaceT/Should non Reptiles appear in Jurassic Park?/@comment-5870856-20130501230807/@comment-3213993-20130502001932

Personally, I think chances would be slim-to-none of cloning anything that lived earlier than the latest Jurassic, comparative genomics and ancestral reconstruction not withstanding. Even that has a limit, since scientists tried to resurrect a 400 million year old protein which turned out to be non-functional.

Anyways, things like mammoths would be out of place in JP4, but it wouldn't exactly ruin it.