Newly Discovered Tiny Fossil: Purgatorius
This shrew-sized mammal is recognized as the oldest known ancestor of all primates, including humans. Initially believed to be confined to northern North America, its range now extends hundreds of kilometers to the south. This week’s article in the Journal of Vertebrate Paleontology, detailed in a recent paper, challenges conventional theories about the biogeography of early primates and suggests that their diversification occurred rapidly following the end-Cretaceous mass extinction.
Shortly after the Cretaceous mass extinction, the earliest known primates like Purgatorius McKivevelli adapted quickly, specializing in an omnivorous diet that included tree fruits and archaic ungulate mammals. Image credit: Andrei Atutin.
The origins and early biogeographical history of primates is a fascinating yet contentious subject. The oldest primates, Purgatorius, are small tree-dwelling mammals that first emerged in North America around 65.9 million years ago.
Previously, Purgatorius fossils were only found in northern regions such as Montana and Saskatchewan, creating an incomplete understanding of their evolutionary history.
Paleontologist Stephen Chester from the City University of New York and his colleagues describe the southernmost fossil of Purgatorius in their new paper.
The specimens were meticulously recovered from ancient sediments in the Coral Bluffs area of the Denver Basin in Colorado.
“This discovery fills a critical gap in our understanding of the geographic distribution and evolution of our earliest primate ancestors after the dinosaur extinction,” Dr. Chester stated.
The fossils analyzed by the team consist of small teeth that display a distinctive combination of features, indicating they may belong to an earlier, previously unidentified species of Purgatorius.
“The presence of these fossils in Colorado reveals that ancient primates likely originated in the north before expanding southward, rapidly diversifying post-end-Cretaceous mass extinction,” Chester explained.
While scientists previously believed Purgatorius was absent from southern regions during this period, new findings suggest that this assumption was primarily due to limited fossil sampling.
“Our results demonstrate that small fossils can easily be overlooked,” Dr. Chester remarked.
“More intensive searches, especially utilizing screen-cleaning techniques, will likely uncover numerous significant specimens.”
The study further questions long-held assumptions about the habitats of early primates.
“The ankle bone of Purgatorius suggested tree-dwelling characteristics, and we initially suspected its absence from southern Montana was due to extensive forest destruction following an asteroid impact 66 million years ago,” Chester noted.
“Yet, our paleobotanical colleagues indicate that plant recovery in North America was rapid, leading us to believe that Purgatorius likely existed further south—we just haven’t looked hard enough.”
_____
Stephen GB Chester et al. “Southernmost Origin of Purgatorius: Insights into the Biogeographic History and Diversification of the Oldest Primates.” Journal of Vertebrate Paleontology, published online March 2, 2026. doi: 10.1080/02724634.2026.2614024
Source: www.sci.news
