Scientists Describe Earliest Primate Fossils

Photo: Lauren DeBey
Photo: Lauren DeBey
February 23, 2021 | Andrea Godinez

Primates diversified right after the mass extinction event that wiped out all dinosaurs except birds.

A new study in the journal Royal Society Open Science documents the earliest-known fossil evidence of any primate. 

A team of 10 researchers from across the U.S. analyzed several fossils of Purgatorius, the oldest genus in a group of the earliest-known primates called plesiadapiforms. These remarkable ancient mammals were small-bodied, and ate specialized diets of insects and fruits that varied across species. This discovery is central to primate ancestry and paints a picture of how life on land recovered after the Cretaceous–Paleogene extinction event 66-million-years ago that wiped out all dinosaurs (except for birds) and led to the rise of mammals. 

Dr. Gregory Wilson Mantilla, Burke Museum Curator of Vertebrate Paleontology and University of Washington Biology professor, co-leads the study with Dr. Stephen Chester of Brooklyn College and The Graduate Center, City University of New York. The team analyzed fossilized teeth found in the Hell Creek area of northeastern Montana. The fossils that are now part of the collections at the University of California Museum of Paleontology, Berkeley, are estimated to be 65.9-million-years-old, about 105,000-139,000 years after the mass extinction event. Based on the age of the fossils, the team estimates that the ancestor of all primates (the group including plesiadapiforms and today’s primates such as lemurs, monkeys and apes) likely emerged by the Late Cretaceous—and lived alongside large dinosaurs.

“It’s mind blowing to think of our earliest archaic primate ancestors—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,” Wilson Mantilla said.  

The fossils include two species of PurgatoriusPurgatorius janisae and a new species described by the team called Purgatorius mckeeveri. Three of the teeth found have distinct features compared to any previously-known Purgatorius species and led to the description of the new species.

The new species Purgatorius mckeeveri is named after Frank McKeever, who was among the first residents of the area where the fossils were discovered, and also the family of John and Cathy McKeever, who have since supported the field work where the oldest specimen of this new species was discovered.

“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,” Co-author and UW Earth and Space Sciences Graduate Student Brody Hovatter said. “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,” Chester said. “It adds to our understanding of how the earliest primates separated themselves from their competitors following the demise of the dinosaurs.”

The team of researchers who collaborated together alongside Gregory Wilson Mantilla and Stephen Chester includes: William Clemens, University of California Museum of Paleontology; Jason Moore, University of New Mexico; Courtney Sprain, University of Florida and University of California Berkeley; Brody Hovatter, University of Washington; William Mitchell, Minnesota IT Services; Wade Mans, University of New Mexico; Roland Mundil, Berkeley Geochronology Center; and Paul Renne, University of California, Berkeley.

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Study Information: Gregory Wilson Mantilla, Stephen Chester, William Clemens, Jason Moore, Courtney Sprain, Brody Hovatter, William Mitchell, Wade Mans, Roland Mundil, Paul Renne. February 24, 2021. Earliest Palaeocene purgatoriids and the initial radiation of stem primates. Royal Society Open Science. DOI: