carapace

The suit -- called a carapace -- is about 70% complete and covers each major region of the body.

"Convergence of the osteoderms across distantly related aetosaurs has been noted before, but the carapace of Garzapelta muelleri is the best example of it and shows to what extent it can happen and the problems it causes in our phylogenetic analyses," Reyes said.

"Turtle growth rates and sizes vary," says Cómbita-Romero, so the team looked at features like the thickness of its carapace and the spots where its ribs were knitting together into solid bone.

"This is a feature uncommon in hatchlings but observed in juveniles. All this information suggests that the turtle likely died with a slightly developed carapace, between 0 to 1 years old, in a post-hatchling stage," he says.

It had stubby limbs and a flattened carapace, suggesting that—unlike modern sea turtles—this ancient reptile lived along shallow coastlines.