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Teeth Prove Our Primate Ancestors Lived Alongside Dinosaurs

By LIDA TUNESI

Way out west in Montana, researchers discovered the oldest fossils of primates to date. Their findings–stemming from the discovery of the creatures’ fossilized teeth–give us the most definitive evidence so far that our earliest primate ancestors lived alongside the giant dinosaurs of the Cretaceous period.

Professor Stephen Chester of Brooklyn College and the Graduate Center was an author on the study, published in Royal Society Open Science.

The fossils come from plesiadapiforms, a now-extinct group of animals that are central to our understanding of primate evolution. With just five fossils of molars to work with, the researchers worked out the creatures’ species, time range, and diets.

Two of the teeth belonged to a Purgatorius janisae, an animal roughly the size of a rat. The other three were also from the Purgatorius genus, but were different enough to warrant the naming of a new species, mckeeveri.

The fossils come from somewhere within 208,000 years after the Cretaceous-Paleogene mass extinction—the event known for wiping out the non-avian dinosaurs about 66 million years ago—according to high-precision dating of the layers around the fossils. In fact, it’s probable that they were alive as little as 105,000 to 139,000 years after the extinction. So while P. janisae and P. mckeeveri lived after the extinction, the researchers inferred that they likely evolved from a common ancestor who was around before it happened.

P. janisae and P. mckeeveri appear to have had shorter molars and more rounded cusps than mammals that only ate insects, lending support to the idea that species in this area also ate fruit. The researchers propose that this omnivore diet, in combination with skeletal features that made them particularly good at hanging out in trees, gave plesiadapiforms an ecological niche that brought them great evolutionary success after the extinction.