Fossil and Paleontology: New Lizard Found

Paleontologists from the University of Alberta discovered fossil remains of a new species of lizard, dating back roughly 80 million years. They found the fossil in the municipality of Cruzeiro do Oeste in southern Brazil, along rock outcrops of a Late Cretaceous desert, and named the new species Gueragama sulamericana. It may represent a missing bridge between lizard species, as a release noted. 

"The roughly 1700 species of iguanas are almost without exception restricted to the New World, primarily the southern United States down to the tip of South America," Michael Caldwell, biological sciences professor from the University of Alberta and one of the study's authors, said in the release. 

However, chameleons and bearded dragons, which are considered iguanas' closest relatives, are all Old World. Lizard knowledge typically spans from acrodontan iguanians -- meaning lizards whose teeth are fused to the top of their jaws -- in the Old World to non-acrodontans in the New World. This new lizard species is the first acrodontan found in South America, which suggests that both groups of ancient iguanians achieved a worldwide distribution before the final break-up of Pangaea, according to the release.

"This fossil is an 80 million year old specimen of an acrodontan in the New World," explained Caldwell. "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."

Distributions of plants and animals from the Late Cretaceous often provide valuable information about Pangaea before it broke apart. 

"This Gueragama sulamericana fossil indicates that the group is old, that it's probably Southern Pangaean in its origin, and that 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 in the release. "South America remained isolated until about five million years ago. That's when it bumps into North America, and we see this exchange of organisms north and south. It was kind of like a floating Noah's Ark for a very long time, about 100 million years. This is an Old World lizard in the new world at a time when we weren't expecting to find it. It answers a few questions about iguanid lizards and their origin."

Their study was recently published in Nature Communications. University of Alberta researchers and scientists in Brazil, conducted the work. They agree that more work will be done, including looking at much older units of rock in order to learn more, said the release. 

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