Despite not being particularly mammal-looking, the earliest true mammals began to rise about 200 million years ago, when dinosaurs were still roaming Earth. However, the therapsids still had important features seen in mammals today. These include a hole on the sides of the skull for the jaw muscle to attach shows and bones that would eventually evolve into inner ear bones mammals are known for.
Now, a team of scientists have found a new fossil that is the oldest of its kind and might even be the oldest therapsid ever discovered. This somewhat dog-like sabertoothed predator is described in a study published December 17 in the journal Nature Communications.
Meet the gorgonopsians
While this new species does not have an official scientific name yet, it is a member of a clade of therapsids called the gorgonopsians.
“Gorgonopsians are more closely related to mammals than they are to any other living animals,” Ken Angielczyk, a study co-author and paleomammaologist at the Field Museum in Chicago, said in a statement. “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.”
The oldest known gorgonopsians lived roughly 265 million years ago. However, the new fossil is from 270 to 280 million years ago, beating them by five to 10 million years.
[ Related: New fossils of tiny, toothy early mammals could be a major missing link. ]
“It is most likely the oldest gorgonopsian on the planet,” Josep Fortuny, a study co-author and head of the Computational Biomechanics and Evolution of Life History group at the Institut Català de Paleontologia Miquel Crusafont (ICP) in Spain, said in a statement.
The fossils were found in Mallorca, a Spanish island in the Mediterranean Sea. At the time of the gorgonopsians, Mallorca was not an island at all. It was part of the supercontinent of Pangea. Here, it likely lived alongside ancient herbivorous reptiles that may have been a part of the gorgonopsians’ diet.
Lots of bones
Among the fossil remains found in Spain, the team studied a nearly complete leg. From this appendage and its vertical position, the team believes that it moved more vertically. Unlike reptiles–who move more horizontally–gorgonopsians had their legs positioned more vertically, possibly moved in a way that was intermediate between reptiles and mammals. This was a more efficient way of walking and even running.
“The large number of bone remains is surprising,” Rafel Matamales, a study co-author and curator of Spain’s Museu Balear de Ciències Naturals (MUCBO | MBCN) said in a statement. “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.”
The bones also allowed the team to reconstruct what the animal looked like and determine a little bit about how it may have lived.
“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.”
From these fierce saber teeth, the team believes that this gorgonopsian species was a top carnivorous predator in its day.
Knowing where we came from
Since this fossil gorgonopsian predates its closest relatives by roughly tens of millions of years, scientists now have a new understanding of when these mammalian ancestors evolved. This crucial stage in mammal’s evolutionary history can even tell us a bit about where our own species came 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.”
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