This saber-toothed carnivore is the oldest mammalian ancestor ever discovered

The origins of mammals are shrouded in mystery, but every fossil trace helps rewrite history. A new discovery on a Mediterranean island calls into question what we know about when and where the ancestors of mammals appeared.

A team of paleontologists has discovered the oldest known mammal ancestor in a pile of fossilized bones from Mallorca, a Spanish island in the Mediterranean. The animal is a roughly 280-million-year-old gorgonopsian, a group of saber-toothed carnivores that roamed the Earth before modern mammals. The discovery of the team, published today in Nature Communicationsshifts the timeline and geography of some of the earliest mammalian ancestors.

Most people notice rise of mammals back to the extinction of the dinosaurs about 66 million years ago. When the asteroid Chicxulub put about 75% of Earth’s species to the sword, including all the dinosaurs, but the ancestors of the birds, the running, running mammals were the survivors left to inherit the planet. But mammalian life began much earlier, with fundamental evolutionary splits that led to animals with backbones, unique holes in their heads, and other differences that set their branch of the tree of life apart from all the others.

The newly examined specimen is fragmentary – consisting of several vertebrae, ribs, a leg bone and parts of the animal’s skull – so the team was unable to identify the animal more precisely than a member of Gorgonopsia. The specimen dates back to at least 270 million years ago, making it the oldest known gorgonops. For context, dinosaurs wouldn’t appear for another 25 million years, rising to prominence during the Triassic period after the catastrophic mass extinction that marked the end of the Permian period.

Like mammals, gorgonopsians are tetrapods—four-legged creatures with a backbone—and more specifically, part of a group of synapsids known as therapsids.

“There’s a big time gap in the therapsid fossil record, between when they’re supposed to have evolved based on our knowledge of synapsid relationships and when they actually appear in the fossil record,” said Josep Fortuny, a paleontologist of the Institut Català de Paleontologia Miquel Crusafont in Spain and senior author of the study, in an email to Gizmodo. “The new specimen helps fill some of that gap.”

“Our discovery is of particular importance for two reasons: first, because it is the first gorgonopsian found at low latitudes,” Fortney said.

Previously, all known gorgonops had been found at higher latitudes – places including Russia and South Africa. They lived when all the continents were part of the supercontinent Pangea, and Majorca was located towards the center of the landmass.

“Secondly, and more importantly, it’s the oldest in the world,” Fortney said. “Thus, finding the oldest gorgonops in the Mediterranean suggests an equatorial origin for this group of animals.”

The fossil was found in an ancient floodplain in central Pangea, where ancestors of mammals and other creatures came to drink.

Mammals are the only living synapsids, but the team’s recent paper shows how early the four-legged vertebrate playbook was drawn up. It also raises questions about exactly where on Earth’s then supercontinent our ancestors first appeared and why. Specimens like the gorgonopsian studied by the team shed light on these fundamental questions about our origins, but there is still a long way to go to fully understand them.