BAR HARBOR, Maine, July 25 (UPI) -- U.S. biologists say they've solved the long-running dispute over whether turtles are more closely related to birds and crocodiles or to lizards.
Turtles have been slow to give up the secrets of their evolution and their place on the evolutionary tree, but paleobiologists at Mount Desert Island Biological Laboratory in Bar Harbor, Maine, say a new technique for analyzing and classifying animals has put turtles firmly with lizards on the family tree of life.
Working with colleagues at Harvard, Yale and Dartmouth, the research team looked at a newly discovered class of molecules called microRNA that can switch genes on and off and regulate protein production and which are also remarkably similar within related animal groups, providing important clues for identification, a MDIBL release said Monday.
"Different microRNAs develop fairly rapidly in different animal species over time, but once developed, they then remain virtually unchanged," said Kevin Peterson, a paleobiologist at MDIBL and Dartmouth College. "They provide a kind of molecular map that allows us to trace a species' evolution."
Peterson worked with Ben King, a bioinformatician at MDIBL, to find microRNAs in the lizard genome.
"We identified 77 new microRNA families, and four of these turned out to also be expressed in the painted turtle," King said. "So we had the evidence we needed to say that turtles are a sister group to lizards and not crocodiles."