New fossil evidence proves that turtles share a recent common ancestor with birds and crocodiles. The discovery may settle a longstanding argument about the origins of turtles, scientists say.
At issue is the evolution of the turtle’s skull. Genetic analysis of molecular sequence data consistently places turtles in a group with birds and crocodilians. This would mean that early turtles had a diapsid skull, with a pair of openings behind each eye that allowed jaw muscles to tighten and flex during chewing.
Yet there was no fossil evidence to confirm that position—until recently.
Researchers found the telltale skull openings in a juvenile example of Eunotosaurus africanus, a 260-million-year-old reptile.
“Eunotosaurus is a ‘cryptic’ diapsid because it closes the skull openings later in life,” says Bhart-Anjan Bhullar, assistant professor of geology and geophysics at Yale University. “Only the fortuitous discovery of these openings in a very young juvenile allowed us to realize this.”
Researchers from the New York Institute of Technology and the Denver Museum of Nature and Science are coauthors of the paper in the journal Nature.
“This process of apparent conflict between DNA and fossils, and eventual reconciliation through new discoveries is a great example of scientific progress, and how our knowledge of vertebrate evolution is itself continually evolving,” says coauthor Daniel Field, a doctoral candidate in geology and geophysics at Yale.
Source: Yale University