This Saber-Toothed Predator Is the Oldest Mammal Ancestor Ever Found

The origin of mammals is shrouded in mystery, but every fossil clue helps rewrite the story. A new discovery on a Mediterranean island is challenging what we know about when—and where—mammal ancestors emerged.

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 Sea. The animal is a roughly 280-million-year-old gorgonopsian, a group of saber-toothed predators that roamed the Earth before modern mammals. The team’s discovery, published today in Nature Communications, pushes back the timeline and the geography of some of mammals’ most ancient ancestors.

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

The recently studied specimen is fragmentary—it consists of several vertebrae, ribs, a leg bone, and parts of the animal’s skull—so the team was not able to identify the animal more precisely than a member of Gorgonopsia. The specimen dates to at least 270 million years ago, making it the oldest known gorgonopsian to date. 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.

Like mammals, the gorgonopsians were tetrapods—four-legged backboned creatures—and more specifically, part of a group of synapsids known as therapsids.

“There is a big time gap in the fossil record of therapsids, between when they are predicted to have evolved based on our knowledge of relationships of synapsids and when they actually show up in the fossil record,” said Josep Fortuny, a paleontologist at the Institut Català de Paleontologia Miquel Crusafont in Spain and senior author of the study, in an email to Gizmodo. “The new specimen helps to fill in part of that gap.”

A gorgonopsian femur. Photo: Anna Solé / Institut Català de Paleontologia Miquel Crusafont

“Our finding is specially relevant for two reasons: first, because it is the first gorgonopsian found in low latitudes,” Fortuny said.

Previously, all known gorgonopsians were found in higher latitudes—places including Russia and South Africa. They lived back when the continents were all part of the supercontinent Pangea, and Mallorca was located towards the center of the landmass.

“Secondly, and even more important, it’s the oldest one worldwide,” Fortuny said. “Thus, finding the oldest gorgonopsian in the Mediterranean suggest an equatorial origin for this group of animals.”

The fossil was found in what was an ancient floodplain in central Pangea, where mammalian precursors and other critters would come to drink.

Mammals are the only living synapsids, but the recent team’s paper showcases 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 cropped up, and why. Specimens like the gorgonopsian investigated by the team shed some light on these fundamental questions of our origins, but there’s still a long way to go towards a complete understanding.