Purgatorius mckeeveri: 65-Million-Year-Old Primate Fossils Uncovered in Montana

Tuesday, March 2, 2021

Shortly after the end-Cretaceous mass extinction, the earliest known primates, such as Purgatorius mckeeveri shown in the foreground, quickly set themselves apart from their competition — like the archaic ungulate mammal on the forest floor — by specializing in an omnivorous diet including fruit found up in the trees. Image credit: Andrey Atuchin.

Paleontologists in the United States have discovered and analyzed the fossilized remains from two species of Purgatorius, the oldest genus in a group of the earliest-known primates called Plesiadapiformes.

Plesiadapiformes first appeared during the Paleocene epoch, between 65 and 55 million years ago, although many were extinct by the beginning of the Eocene epoch.

These ancient primates were small-bodied and ate specialized diets of insects and fruits that varied by species.

They are crucial to understanding the evolutionary and ecological origins of primates, treeshrews, and colugos as well as the traits that separate those groups from other mammals.

Five new isolated plesiadapiform teeth were recovered from the Harley’s Point locality of the Fort Union Formation in northeastern Montana.

The fossils are estimated to be 65.9 million years old, about 105,000 to 139,000 years after the end-Cretaceous mass extinction event.

Two three from the sample are from a previously known species of plesiadapiform called Purgatorius janisae. Three other specimens represent a new species named Purgatorius mckeeveri.

“It’s mind blowing to think of our earliest archaic primate ancestors,” said co-lead author Professor Wilson Mantilla, a vertebrate paleontologist in the Department of Biology at the University of Washington and the Department of Paleontology at the Burke Museum of Natural History and Culture.

“They were some of the first mammals to diversify in this new post-mass extinction world, taking advantage of the fruits and insects up in the forest canopy.”

High resolution CT scans of fossilized teeth and jaw bones of Purgatorius. Image credit: Gregory Wilson Mantilla / Stephen Chester.

Based on the age of the fossils, Professor Mantilla and colleagues estimate that the ancestor of all primates — including plesiadapiforms and today’s primates — likely emerged by the Late Cretaceous epoch and lived alongside large dinosaurs.

“This was a really cool study to be a part of, particularly because it provides further evidence that the earliest primates originated before the extinction of non-avian dinosaurs,” said co-author Brody Hovatter, a graduate student in the Department of Earth and Space Sciences at the University of Washington.

“They became highly abundant within a million years after that extinction.”

“This discovery is exciting because it represents the oldest dated occurrence of archaic primates in the fossil record,” added co-lead author Dr. Stephen Chester, a researcher at Brooklyn College and the City University of New York.

“It adds to our understanding of how the earliest primates separated themselves from their competitors following the demise of the dinosaurs.”

The research was published in the journal Royal Society Open Science.


Gregory P. Wilson Mantilla et al. 2021. Earliest Palaeocene purgatoriids and the initial radiation of stem primates. R. Soc. open sci 8 (2): 210050; doi: 10.1098/rsos.210050

Source: www.sci-news.com/