The Trouble With Turtles: Paleontology at a Crossroads

Scientists debate whether modern turtles are more closely related to snakes and lizards or birds and crocodiles.

by Naomi Lubick

Traditional paleontological research has been upended over the past few decades, as less traditional fields, such as genomics and developmental biology, have weighed in on vertebrate evolution. Researchers have examined the lingering color elements in dinosaur feathers, the genetics of woolly mammoths, purported proteins and blood from dinosaurs, and other ancient fossil signatures using modern tools. But the question of turtle evolution has remained resistant to both traditional and novel methods.

More than 300 species of turtles exist today, but where they came from isn’t entirely clear. Turtles are the last big living vertebrate group to be placed firmly on the tree of life, and the arguments are getting messy. Three fields in particular — paleontology, developmental biology and microbiology/genomics — disagree about how, and from what, turtles may have evolved.

Traditional paleontologists have placed turtles, which are indisputably reptiles, in relation to a group of mostly extinct reptilian animals called anapsids, which don’t have holes in their skulls; however, analyses in the 1990s put turtles in the diapsid camp, which originally had two holes in their skulls, and closer to modern reptiles like snakes. Morphology places them near the group made up of lizards and birds and crocodiles…

(read more: EARTH Magazine)

images: T - Kathleen Cantner, AGI.; Bottom 3 - Tyler Lyson, NMNH