New Fossil of Extinct Reptile May be the Missing Link for Lizard Evolution

First Posted: Aug 27, 2015 07:24 AM EDT
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A new species of lizard may just be the missing link for lizard evolution. Scientists have discovered a fossil lizard, named Gueragama sulamericana, which dates back to the outcrops of a Late Cretaceous desert that existed about 80 million years ago.

"The roughly 1,700 species of iguanas are almost without exception restricted to the New World, primarily the Southern United states down to the tip of South America," said Michael Caldwell, one of the researchers, in a news release.

With that said, the iguana's closest living relatives, which include chameleons and bearded dragons, are all from the Old World. The new lizard species, though, is the first acrodontan (teeth are fused to the top of their jaws, which dominated the Old World) to be found in the New World.

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

The fossil itself indicates that the group is old, and that it's probably Southern Pangaean in origin. After the continent broke up, the acrodontans and chameleon group dominated the Old World and the iguanid side arose out of the acrodontan lineage that was left alone in South America.

"Each question only rattles the questions harder," said Caldwell. "The evolution of the group is much older than has been previously thought, which means we can push an acrodontan to 80 million years in South America. We now need to focus on much older units of rock if we're going to find the next step in the process."

The findings are published in the journal Nature Communications.

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