Researchers working at rock outcrops in a Late Cretaceous desert in South America have discovered a new species of extinct lizard that lived 80 million years ago. Gueragama sulamericana, described in Nature Communications this week, overturns what we know about lizard evolution.
While acrodontans (who have teeth fused to their jaws) ruled the Old World, non-acrodontans thrived in the New World. This new species, Gueragama sulamericana from what’s now Cruzeiro do Oeste in southern Brazil, is the first acrodontan found in South America. That means both groups of ancient reptiles achieved an impressive worldwide distribution before the final break up of the supercontinent Pangaea.
"It's a missing link in the sense of the paleobiogeography and possibly the origins of the group, so it's pretty good evidence to suggest that back in the lower part of the Cretaceous, the southern part of Pangaea was still a kind of single continental chunk," study co-author Michael Caldwell from the University of Alberta said in a statement. "Guera" is native Brazilian Tupi-Guarani for "ancient" and "sulamericana" means "from South America" in Portuguese. Its partial lower jawbone is pictured to the right.
Distributions of Late Cretaceous plants and animals reflect a time when Pangaea was still whole. With more than 1,700 species, the reptile suborder iguania — which includes critters like iguanas, chameleons, anoles, and spiky horned lizards — is one of the most diverse groups of lizards worldwide. With few exceptions, all iguanas are restricted to the New World, especially between the southern U.S. and the southernmost tip of South America. Yet their closest relatives, including chameleons and bearded dragons, are all Old World species.
Gueragama sulamericana is Southern Pangaean in its origin. "After the break up, the acrodontans and chameleon group dominated in the Old World, and the iguanid side arose out of this acrodontan lineage that was left alone on South America," Caldwell said. South America remained isolated until about five million years ago, when it bumped into North America. That’s when we began to see a north-south exchange of plants and animals again. "It was kind of like a floating Noah's Arc for a very long time, about 100 million years," he added. "This is an Old World lizard in the New World at a time when we weren't expecting to find it."
Image in the text: Tiago Simoes and Adriano Kury