Purgatorius

Hell Creek, 66 million years ago.

Art I made of a Tyrannosaurus fighting a Triceratops, along with a few creatures in the background.

If you don’t know what Purgatorius is, it’s the oldest known primate, or stem-primate.

According to Wikipedia, it lived in the Paleocene, but the oldest fossils are literally found on the Cretaceous-Paleogene boundary in the Hell Creek Formation, 66 million years ago. So is it possible that Purgatorius could’ve evolved earlier and existed with the dinosaurs of Hell Creek for a short about of time? (Ankylosaurus, Pachycephalosaurus, Triceratops, Tyrannosaurus, etc)