Ancient iguana fossil shines light on lizard evolution

EDMONTON, Alberta, Aug. 27 (UPI) -- A new fossil uncovered in Brazil has provided link between the lineages of Old and New World lizards, shining light on the reptile's early evolution.

The lizard is a new species, named Gueragama sulamericana, discovered by University of Alberta paleontologists in Southern Brazil. Its presence helps explain two distinctions that have long puzzled scientists.

Most iguanas hail from South America (the New World). But the iguana's closest relatives, chameleons and bearded dragons, all hail from the Old World (Europe and Asia).

Additionally, iguanas are divided into two main lineages -- acrodontan and non-acrodontan. Acrodontan iguanas, those with teeth fused to their upper jaw, populate the Old World, while non-acrodontan dominate the New World.

The newly discovered species, however, is an acrodontan lizard, the first ever found in the New World. The discovery suggests the lineage of iguanas dates back to a time when the Old and New World were side-by-side, existing as Pangea.

"This fossil is an 80-million-year-old specimen of an acrodontan in the New World," Michael Caldwell, a biological sciences professor at Alberta, said in a press release. "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."

Caldwell is the lead author of a new study, published in the journal Nature Communications.

But as usual, as answers emerge, so too do new questions.

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