A new analysis of a 90-million-year-old reptile skull has helped scientists from the University of Edinburgh discover how snakes lost their limbs. Using CT scans of the fossil and those from modern reptiles, the team concluded that snakes lost their legs around the same time that their ancestors adapted to live and hunt in burrows. Previous findings suggested that snakes lost their limbs in order to evolve to life in the sea.
"How snakes lost their legs has long been a mystery to scientists, but it seems that this happened when their ancestors became adept at burrowing," Hongyu Yi, a member of the research team, said in a press release. "The inner ears of fossils can reveal a remarkable amount of information, and are very useful when the exterior of fossils are too damaged or fragile to examine."
The study used CT scans to analyze the inner ear of the Dinilysia patagonica, a species of reptile that is closely linked to modern snakes. Using 3-D virtual models, they compared the inner ears of the fossils with modern snakes and lizards, leading to the discovery of a structure within the inner ear of animals that actively burrow. This adaptation likely helps burrowers detect prey and predators and was not found in modern snakes that live in water or on the Earth's surface.
"This discovery would not have been possible a decade ago - CT scanning has revolutionised how we can study ancient animals," said Mark Norell, co-author of the study. "We hope similar studies can shed light on the evolution of more species, including lizards, crocodiles and turtles."
The findings shed light on the evolution of the snake and also confirm that the Dinilysia patagonica is the largest burrowing snake currently known. Furthermore, the information could be used to answer questions about the hypothetical ancestral species of modern snakes.