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Fossil scan reveals how snakes became limbless

By
Marilyn Malara
Image and representation of brain case and inner ear of Dinilysia patagonica fossil, which scientists at the University of Edinburgh and American Museum of Natural History have used to show that modern snakes lost their legs when their ancestors became expert burrowers. Photo by Hongyu Yi/University of Edinburgh
Image and representation of brain case and inner ear of Dinilysia patagonica fossil, which scientists at the University of Edinburgh and American Museum of Natural History have used to show that modern snakes lost their legs when their ancestors became expert burrowers. Photo by Hongyu Yi/University of Edinburgh

EDINBURGH, Scotland, Nov. 28 (UPI) -- Comparisons between modern snake skulls and the 90 million-year-old fossil suggest snakes lost their limbs in order to burrow on land.

Using CT scans to study the inner ear cavity of the fossilized Dinilysia patagonica skull, scientists at the University of Edinburgh found the structure of the canal is similar to modern burrowing serpents, but not those that live above ground or in water.

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The findings suggest the Dinilysia patagonica, at two meters long, is the largest burrowing snake ever known.

"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," lead researcher Dr. Honguy Yi of the University of Edinburgh's School of GeoSciences 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."

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The study is published in Science Advances and was sponsored by the Royal Society in Scotland.

Scientists at Yale concluded earlier this year snakes indeed evolved on land, not in water like once assumed. Through analysis of snake genomes, anatomy and fossils, the researchers constructed a family tree of serpents suggesting the most recent common ancestor of today's snakes had lost its forelimbs but still had tiny hind limbs some 128 million years ago.

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"It would have first evolved on land, instead of the sea," said the Yale study's co-author Daniel Field of the world's earliest snakes. "Both of those insights resolve longstanding debates on the origin of snakes."

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