Uncovered Oldest Known Mammal Precursor with Saber-Like Teeth
The origin of mammals has remained enigmatic, but every fossil finding contributes to rewriting the narrative. A groundbreaking discovery on a Mediterranean island is contending with our existing beliefs about when and where mammal ancestors emerged.
A group of paleontologists has stumbled upon the oldest recognized mammal ancestor in a heap of fossilized bones hailing from Mallorca, a Spanish island nestled in the Mediterranean Sea. The creature is an approximately 280-million-year-old gorgonopsian, a class of saber-toothed predators that inhabited the Earth prior to modern mammals. The researchers' discovery, which saw publication today in Nature Communications, moves back the timeline and geography of some of mammals' most primitive ancestors.
Many attribute the surge of mammals to the downfall of dinosaurs roughly 66 million years ago. When the Chicxulub asteroid wiped out about 75% of Earth's species, including all dinosaurs apart from their avian relatives, the rudimentary, scurrying mammals endured as the remaining inhabitants left to claim the Earth. However, mammalian life began much earlier, stemming from fundamental evolutionary splits that spawned creatures with spinal columns, unique cranial features, and other traits that distinguished their branch on the tree of life from all others.
The scrutinized specimen is fragmented – it is composed of several spinal vertebrae, ribs, a leg bone, and sections of the animal's skull – thereby preventing the researchers from identifying the animal more precisely than as a gorgonopsian. The specimen dates to at least 270 million years ago, establishing it as the oldest known gorgonopsian in existence. For context, dinosaurs wouldn't make their debut for another 25 million years, becoming dominant during the Triassic Era after the catastrophic mass extinction that signaled the end of the Permian.
Like mammals, the gorgonopsians were tetrapods – four-legged vertebrates – and more specifically, a part of the synapsid family known as therapsids.
"There is a significant gap in the fossil record concerning therapsids, between when they are predicted to have evolved based on our understanding of synapsid relationships and when they actually materialize in the fossil record," said José Fortuny, a Spanish paleontologist from the Institut Català de Paleontologia Miquel Crusafont and the study's senior author, in an email to Gizmodo. "The new specimen helps fill a portion of that gap."
The team's finding is particularly significant for two reasons: first, because it is the first gorgonopsian discovered in low latitudes. Previously, all known gorgonopsians were uncovered in higher latitudes, such as Russia and South Africa. At that time, the continents were united as a supercontinent called Pangea, and Mallorca was situated at the center of the landmass.
"Secondly, and even more crucial, it's the oldest one worldwide," Fortuny pointed out. "Discovering the oldest gorgonopsian in the Mediterranean implies an equatorial origin for this group of animals."
The fossil was unearthed in what was an ancient floodplain in central Pangea, where mammalian precursors and other wildlife would congregate to quench their thirst.
The discovery of the oldest recognized mammal ancestor as a gorgonopsian in Mallorca challenges the notion that mammals mainly emerged after the dinosaur extinction. This ancient gorgonopsian, with its saber-teeth and four-legged structure, represents a significant piece of evidence for the early evolution of mammals, as technology and science continue to uncover the secrets of the future in the depths of our past.
This gorgonopsian's presence in lower latitudes, as opposed to previous findings in higher latitudes, suggests that the future diversity of mammals may have had a more equatorial origin than previously thought, a fascinating insight for both scientists and those interested in the history of life on Earth.
