SCIENTIFIC EDUCATIONAL CENTER science idea

The first true mammals evolved roughly 200 million years ago, during the early days of the dinosaurs. But mammals are the last surviving members of an older group, called the therapsids. At first glance, many therapsids weren’t obviously mammal-like , but they also had subtle features that we recognize in mammals today, like a hole on the sides of their skull for the jaw muscle to attach and structures on their jaw bones that would eventually evolve into mammals' distinctive middle ear bones. In a new paper in the journal Nature Communications, scientists announce the discovery of a fossil therapsid that’s the oldest of its kind, and maybe the oldest therapsid ever discovered: a vaguely dog-like saber-toothed predator. 

The new fossil, which doesn’t have a species name yet, is a member of a group called the gorgonopsians. “Gorgonopsians are more closely related to mammals than they are to any other living animals,” says Ken Angielczyk, the Field Museum’s MacArthur Curator of Paleomammalogy in the Negaunee Integrative Research Center and a co-author of the paper. “They don’t have any modern descendents, and while they're not our direct ancestors, they're related to species that were our direct ancestors.”

Until now, the oldest known gorgonopsians lived roughly 265 million years ago. However, the new fossil is from 270-280 million years ago. “It is most likely the oldest gorgonopsian on the planet,” says Josep Fortuny, senior author of the article and head of the Computational Biomechanics and Evolution of Life History group at the Institut Català de Paleontologia Miquel Crusafont (ICP) in Spain.

The fossils were found in Mallorca (also sometimes spelled Majorca), a Spanish island in the Mediterranean Sea. But in the time of the gorgonopsians, Mallorca was part of the supercontinent of Pangea. 

“The large number of bone remains is surprising. We have found everything from fragments of skull, vertebrae, and ribs to a very well-preserved femur. In fact, when we started this excavation, we never thought we would find so many remains of an animal of this type in Mallorca,” explains Rafel Matamales, curator of the Museu Balear de Ciències Naturals (MUCBO | MBCN), research associate at the ICP, and first author of the article.

These bones allowed the researchers to reconstruct what the animal looked like and a little about its life. “If you saw this animal walking down the street, it would look a little bit like a medium-sized dog, maybe about the size of a husky, but it wouldn’t be quite right. It didn’t have any fur, and it wouldn’t have had dog-like ears,” says Angielczyk. “But it’s the oldest animal scientists have ever found with long, blade-like canine teeth.” These saber teeth suggest that this gorgonopsian was a top predator in its day.

The fact that this gorgonopsian predates its closest relatives by tens of millions of years changes scientists’ understanding of when therapsids evolved, an important milestone on the way to the emergence of mammals, and in turn it tells us something about where we come from.

“Before the time of dinosaurs, there was an age of ancient mammal relatives. Most of those ancient mammal relatives looked really different from what we think of mammals looking like today,” says Angielczyk. “But they were really diverse and played lots of different ecological roles. The discovery of this new fossil is another piece of the puzzle for how mammals evolved.”

JOURNAL

Nature Communications

DOI

10.1038/s41467-024-54425-5 

IMAGE: 

A RECONSTRUCTION OF THE OLDEST KNOWN GORGONOPSIAN IN LIFE.

view more 

CREDIT: ILLUSTRATION © HENRY SUTHERLAND SHARPE.

https://www.eurekalert.org