Dinosaurs get all the glory. But aetosaurs, heavily armored cousins ​​of modern crocodiles, dominated the world before dinosaurs. These Triassic reservoirs appeared in a variety of shapes and sizes before becoming extinct about 200 million years ago. Today, its fossils are found on all continents except Antarctica and Australia.

Scientists use the bony plates that made up Aetosaurus armor to identify different species, and they generally don’t have a lot of fossil skeletons to work with. But the new study, led by researchers at the University of Texas at Austin, focused on Aetosaurus’ armor, which had most of its major parts intact.

The garment, called the shell, is about 70% complete and covers every major part of the body. The article was published on: Anatomical Registration.

“We have elements that extend from the back of the neck and the shoulder area to the tip of the tail,” said William Reyes, a postdoctoral researcher at Jackson State University’s School of Geological Sciences who led the study. “You usually find very limited supplies.”

Using this armor, Reyes and his colleagues identified the specimen as a new species of Aetosaurus, which they named Garzapelta muelleri. The name “garza” recognizes Garza County in northwestern Texas, where Aetosaurus was found, and “pelta” is the Latin word for shield, referring to Aetosaurus’ heavily reinforced body. The species name “muelleri” honors paleontologist Bill Mueller, who first discovered it.

Garzapelta lived about 215 million years ago and was similar to the modern American crocodile, but with much larger armor.

“Take a modern alligator and turn it into an armadillo,” Reyes said.

The bone plates covering Garzapelta and other aetosaurs are called osteoderm. They were embedded directly into the skin and joined together like a mosaic to form the armor. In addition to its body covered in bony plates, Garsapelta’s sides were surrounded by curved spikes that offered another level of protection against predators. Although today’s crocodiles are carnivorous, scientists believe that aetosaurs were primarily omnivores.

Garzapelta’s spines are very similar to those found in other aetosaur species, but surprisingly the researchers found that the two species are only distantly related. The similarities they found are an example of convergent evolution, the independent evolution of similar traits in different species. A classic example of this phenomenon is the development of flight in insects, birds, mammals, and extinct pterosaurs.

According to Reyes, a number of unique features in Garsapelta’s plates clearly indicate that it is a new species. They vary from the way the plates meet to the unique ridges and protrusions on the bones. But figuring out where Garzapelta fits into the larger aetosaur family tree has been more difficult. Depending on which part of the armor the researchers emphasized in their analysis, Garzapelta found herself in very different places. The armor extending down the back resembled the armor of one species, while the spikes in the middle resembled the armor of another species.

Once the researchers determined that the spines evolved independently, they were able to determine where Garzapelta fit in best among other aetosaur species. Still, Reyes said the study shows how convergent evolution can complicate things.

“Osteoderm convergence between distantly related aetosaurs has been seen before, but the shell of Garzapelta muelleri is a prime example of this and demonstrates the extent to which this could occur and the problems it causes in our phylogenetic analysis,” Reyes said.

Garzapelta is part of the Texas Tech University fossil collection. It spent most of the last 30 years on the shelf before Reyes stumbled upon it during his visit. University and museum collections are a critical part of making this type of research possible, said Bill Parker, an aetosaur expert and park paleontologist at Petrified Forest National Park who was not involved in the research.

“These samples were not just excavated at the site yesterday,” he said. “They’ve been sitting in a museum for decades, and it just takes someone like Will to come along and finally decide to study them and bring them to life.”

In addition to different species having different armor, it is possible that the age or sex of the animal can also affect the appearance of the armor. Reyes is currently exploring these questions by examining aetosaur fossils in the Jackson School collection, many of which were found during excavations by the Works Progress Administration in the 1940s.

The study was co-authored by Jeffrey Martz, an associate professor at the University of Houston Downtown, and Brian Small, a research assistant at the Texas Tech University Museum.