Purgatorius (Greek for "one in purgatory"); pronounced per-gah-TORE-ee-us
Woodlands of North America
Late Cretaceous (65 million years ago)
Size and Weight:
About 6 inches long and a few ounces
Small size; primate-like teeth
Most of the prehistoric mammals of the late Cretaceous period looked pretty much the same--small, quivering, mouse-sized creatures that spent most of their lives high up in trees, the better to avoid rampaging raptors and tyrannosaurs. On closer examination, though, especially of their teeth, it's clear that these mammals were each specialized in their own distinct way. What set Purgatorius apart from the the rest of the rat pack is that it had distinctly primate-like teeth, leading to speculation that this tiny creature may have been directly ancestral to modern-day chimps, rhesus monkeys, and humans--all of whom had the chance to evolve only after the dinosaurs went extinct and opened up some valuable breathing room for other types of animals.