This Armored Ancestor Of Modern Crocodiles Roamed Earth Over 200 Million Years Ago

An artist's interpretation of the newly identified aetosaur *Garzapelta muelleri* (Credit: Márcio L. Castro)

Researchers from the University of Texas (UT) Austin recently announced the discovery of a new aetosaur species. These prehistoric relatives of modern crocodiles, which ruled the world before dinosaurs, came in many shapes and sizes. The heavily armored creatures went extinct around 200 million years ago. However, their fossils can still be found on every continent except Antarctica and Australia.

Paleontologist Bill Mueller unearthed the newfound species in Garza County, Texas, in 1989. The fossil was added to the collection at Texas Tech University, where it remained for nearly three decades. The fossil received renewed attention when William Reyes, a doctoral student at UT Austin, discovered it during a visit.

Reyes was drawn to the unusually large and well-preserved dorsal carapace, or back armor. Scientists rely on the bony plates that make up aetosaur armor to identify different species. But there are usually limited fossil skeletons to study. However, this specimen was almost 70 percent intact, covering each major region of the body.

"We have elements from the back of the neck and shoulder region all the way to the tip of the tail," said Reyes. "Usually, you find very limited material."

The top image is the fossil, as seen from above. The bottom image is the fossil seen from the side (Credit: William Reyes)

Reyes and his colleagues named the ancient reptile Garzapelta muelleri. The genus name combines "Garza" from Garza County, where it was found, with "pelta," meaning "shield" in Latin. The species name honors Mueller, who passed away in 2019.

The researchers revealed their findings on March 14, 2024. They believe that the stocky-limbed G. muelleri was a medium-sized aetosaur. It had several unusual features, including a unique arrangement of bony plates that formed bumps and ridges on its skeleton. The reptile's sides were covered with curved spikes, offering another layer of protection from predators. The spikes were similar, but not identical, to those found on another aetosaur species. This led the UT Austin team to conclude that G. muelleri was an entirely new species of aetosaur.