New Species of Dog-Sized Dinosaur Found in Chile Had 'Really Bizarre Tail'

Scientists found a new species of dinosaur in Chile after they discovered fossils the size of a dog with an unusual tail, the Associated Press reported.

University of Chile paleontologist Alex Vargas said the tail was something he had never seen on an animal. He described it in a study in the journal Nature and said it consists of seven pairs of "blades" that jetted out sideways. Vargas said the tail would have been used as an "unusual weapon."

It was challenging for researchers to figure out what kind of species the dinosaur was. They thought it ate plants and had a combination of traits from other species, but it was its tail that pointed them in the right direction.

Researchers named the species stegouros elengassen after its tail and back end seemed similar to a stegosaurus.

The dinosaur has a bird-like snout and stretches about 6 feet in length, but the height is only up to a person's thighs, Vargas said.

"Books on prehistoric animals for kids need to update and put this weird tail in there....It just looks crazy," he said.

The fossil of the new species was found in the southern region of Chile and is estimated to be about 72 million to 75 million years old. Vargas said the dinosaur appears to be an adult based on how the bones are fused.

For more reporting from the Associated Press, see below.

Dinosaur, Fossil, Chile
Fossils found in Chile are from the bizarre dog-sized dinosaur species with a unique slashing tail weapon, scientists reported on December 1, 2021. Above, an illustration of a Stegouros provided by Mauricio Alvarez. Mauricio Alvarez/AP Photo

The tail was probably for defense against large predators, which were also likely turned off by armor-like bones jutting out that made stegouros "chewy," Vargas said.

Not only is this "a really bizarre tail," but it is from far southern Chile, "a region that hasn't yielded these types of animals before," said Macalester College biologist Kristi Curry Rogers, who wasn't part of the study.

Some dinosaurs had spiked tails they could use as stabbing weapons and others had tails with clubs. The "blades" on the tail of the new species acted like a slicing weapon used by ancient Aztec warriors, said Vargas, the lead author.

"It's a really unusual weapon," he said.

After Vargas and his team examined the pieces of skull and did five different DNA analyses, they concluded it was only distantly related to the stegosaurus. Instead, it was a rare Southern Hemisphere member of the tank-like ankylosaur family of dinosaurs. (Though the stegouros name stuck and can be easily confused with the more well-known stegosaurus.)

Vargas called it "the lost family branch of the ankylosaur."

The fossil was found with its front end flat on its belly and the back end angled down to a lower level, almost as if caught in quicksand, Vargas said.

"We're just scratching the surface when it comes to a comprehensive understanding of dinosaur diversity," Rogers said. "Stegourus reminds us that if we look in the right places at the right times, there is so much more still to discover."

Stegouros, Fossil, Chile
Scientists found a new species of dinosaur in Chile after they discovered fossils the size of a dog with an unusual tail. This illustration provided by Luis Perez Lopez shows a Stegouros. Luis Perez Lopez/AP Photo