Turtles More Closely Related to Birds Than to Lizards, According to Landmark Genetic Study

Turtles, like birds, are relatives of dinosaurs. (Photo: Jonathan Zander/Wiki Commons).

They might not look it, but turtles are more closely related to birds than they are to lizards, according to a new landmark genetic study by researchers at the California Academy of Sciences, reports Phys.org.

The study helps to clear up a debate that has been raging among scientists for decades regarding turtle evolution. Using a new genetic sequencing technique called Ultra Conserved Elements (UCE), researchers were able to finally put to rest the idea that turtles are most closely related to lizards and snakes. Their findings instead show that turtles belong in their own group, "Archelosauria," along with their true relatives: birds, crocodiles and dinosaurs.

UCE has only been around since 2012, so scientists are only beginning to utilize this powerful tool for the genetic mapping of vertebrates. It is revolutionizing our ability to understand the evolutionary tree of life.

"Calling this an exciting new era of sequencing technology is an understatement," said Brian Simison, PhD, Director of the Academy's Center for Comparative Genomics that analyzed the study's massive amount of data.

"In the space of just five years, reasonably affordable studies using DNA sequencing have advanced from using only a handful of genetic markers to more than 2,000--an unbelievable amount of DNA," Simison added. "New techniques like UCE dramatically improve our ability to help resolve decades-long evolutionary mysteries, giving us a clear picture of how animals like turtles evolved on our constantly-changing planet."

The findings also help to clear up a long-time evolutionary mystery within the turtle group: Where to place soft-shell turtles? Softshell turtles are oddballs among turtles, with no scales and showcasing snorkel-like snouts. The study found that these turtles emerge from an ancient line that makes them only distant relatives of other turtles. Their long, independent evolutionary history helps explain their bizarre appearance.

The results of the UCE study are also consistent with the time and space patterns by which turtle species appear in the fossil record, which reinforces the accuracy of the method.

"These new testing techniques help reconcile the information from DNA and fossils, making us confident that we've found the right tree," said study coauthor James Parham.