Primates appeared almost immediately after dinosaurs disappeared, new research finds

A training renowned for producing T. rex fossils has now provided the oldest evidence of primates in the fossil record, which is being hailed as a significant find.

Jaws and an assortment of teeth found in the Hell’s Creek Formation in northeastern Montana are the oldest primate fossils ever to be found, according to a new search published in Royal Society Open Science.

Dating from around 65.9 million years ago, these animals lived between 105,000 and 139,000 years only after the Cretaceous-Paleogene extinction, during which an asteroid wiped out most plant and animal species. on earth. The new paper was co-edited by Gregory Wilson Mantilla of the University of Washington and Stephen Chester of Brooklyn College and the City University of New York.

“This is an important study because it documents the earliest primates ever discovered, pushing the date of the oldest primates back to the earliest Paleocene, in addition to establishing greater diversity as well,” Eric Sargis, professor of anthropology at Yale University, which is not affiliated with the new study, said in an email.

Indeed, the age of these fossils is significant, because it suggests the ancestor of all primates, extinct and extant, lived in the Mesozoic, more precisely in the Upper Cretaceous. Prior to this discovery, the oldest evidence of stem primates, or primates, in the fossil record dates back to the first 300,000 to 500,000 years of the Paleocene (the post-Mesozoic era).

Newly discovered teeth and jaws belong to two different species: P. janisae and P. mckeeveri. Both species belong to Purgatorius, the oldest known genus associated with primates. Other members of this group include P. unio and P. ceratops, and they are all considered to be plesiadapiformes – a stem group of primates that includes Purgatorius and where all modern primates like monkeys, monkeys (including you), and lemurs are descended from.

P. janisae was already known to paleontologists, but P. mckeeveri is a newly described species named after a family that supported fieldwork in this area. Three teeth with features never seen before Purgatorius allowed scientists to report the discovery of a new species.

The team studied these extinct creatures by examining a large collection of fossils at the University of California Museum of Paleontology, which houses the largest collection of P. janisae fossils. They also had other epoxy castings Purgatorius fossils to work with, as well as enlarged 3D models printed from microCT scans. The team also used a technique called “geometric morphometry” to scan and compare the characteristics of fossils to other known species.

“This work was done with a large team who brought distinct and essential skills to this research, from geochronologists who were able to frame the age of these fossils to geologists who were able to decipher how these fossils were deposited,” said Mantilla in an email. “We also could not have done this work without the help of generous colleagues from the museums where we worked. [with] and landowners in Garfield County, MT, who allowed us to work on their land. It was a big team effort.

Scientists do not yet know the exact timing of the emergence of Purgatorius, but the “fact that there are two species” that arose so soon after mass extinction “implies that their ancestor was older than the two descendant species,” Mantilla wrote. It is increasingly likely that the ancestor of the plesiadapiformes “first appeared in the Late Cretaceous rather than the Paleocene,” he said, meaning that the first proto-primates would have rubbed elbows with dinosaurs.

As for the precursor of Purgatorius, it’s still a mystery. As Mantilla explains, some North American fossil species dating from the Late Cretaceous have been proposed to be ancestral to Purgatorius, including rat-like Gypsonictops. It is probably more likely that “we have not yet found the ancestor in the fossil record,” he added.

These tiny placental mammals looked a lot like squirrels, but Purgatorius, like other plesiadapiforms, “share dental characteristics with other primates,” Sargis said, adding that their teeth looked like primates and not rodents.

I asked Chester what makes a primate a primate, to which he replied:

This is an excellent question and a central issue for all researchers studying the origins of primates. Until we fully understand what makes a primate a primate, it’s hard to know when our primate ancestors diverged from other mammals. Nowadays, many primates have traits associated with grabbing, jumping, a plant-based diet, improved vision, and intelligence. However, we do know from the fossil record that not all of these traits evolved at the exact same time. As paleontologists, we can trace this combination of traits back to extinct primates since the early Eocene around 56 million years ago. But as you go back in time to the earliest Paleocene, around 66 million years ago, it’s clear that our first parents of primates like Purgatorius had some of these traits, but not all of them. Two important suites of features that evolved very early in the evolution of primates were skeletal features like grasping hands and feet for life in trees, and dental features like specialized molars for eating non-leafy plant products like trees. fruits. This combination of traits allowed our first primate parents to separate themselves from their competition right after the dinosaurs disappeared.

As the new study shows, Purgatorius were among the first mammals to succeed in the Paleocene, appearing “shortly after the disaster that wiped out non-avian dinosaurs,” Mantilla explained. “They had a few adaptations that allowed them to thrive in the aftermath of this disaster. First, they were arboreal – they spent most of their time in trees – and second, they had teeth that allowed them to feed on fruits and insects.

These traits, it seems, allowed Purgatorius “Grow and become an important part of the earth’s ecosystem within a million years after the mass extinction event,” he added.

Mammals first appeared in the Upper Triassic, around 300 million years ago (we’ve been around for a while!). That primates were able to thrive after the extinction of non-avian dinosaurs is not a huge surprise. Indeed, mammals quickly took over after the terrible lizards were extinct, giving birth to the age of mammals about 10 million years after the Cretaceous-Paleogene extinction event.

After living in the shadow of dinosaurs for hundreds of thousands of years, our time has finally come.