Lizards and snakes belong to a family of animals called squamates, and today there are almost 10,000 different species slithering around the world's deserts, backyards, forests and mountains. But who is the mother of them all? Scientists have now pinned the origins of this family on a 240-million-year-old fossil that fills in some of the long-time blanks in their early evolutionary history.

The famous Dolomites mountain range in Italy's north is home to huge swathes of exposed rock, some of which is sand and clay that dates back to around 240 million years ago. It was here in the early 2000s that paleontologists discovered a beautifully preserved fossil resembling a lizard-like reptile, which was dubbed Megachirella wachtleri. But they couldn't be certain of where, or if, it fit into the squamate family tree.

Now an international team of scientists have cracked the code. They did so by first assembling the largest reptile dataset ever created, and then used previously unavailable technologies to carry out micro CT scans of the fossil and create a high-resolution 3D model of its anatomy.

This revealed previously unknown physical features, including of the animal's underside that had been embedded in the rock. This new knowledge of Megachirella's anatomy, along with their comprehensive new dataset, enabled the scientists to accurately place the fossil in the reptile family tree. Its new home? At the beginning of the squamate branch, single-handedly dragging the timeline for lizards back 75 million years.

"The specimen is 75 million years older than what we thought were the oldest fossil lizards in the entire world and provides valuable information for understanding the evolution of both living and extinct squamates," says Tiago Simões, lead author of the study and PhD student from the University of Alberta in Canada.

Today squamates are among the largest groups of vertebrates on Earth, but despite their prominence there is much to learn about their early evolutionary history. Now, with a detailed picture of the so-called Mother of all Lizards, scientists will be better equipped to explore what the first forms of these creatures looked like.

"Fossils are our only accurate window into the ancient past," says study co-author, Dr Michael Caldwell, also from the University of Alberta. "Our new understanding of Megachirella is but a point in ancient time, but it tells us things about the evolution of lizards that we simply cannot learn from any of the 9,000 or so species of lizards and snakes alive today."

The research was published in the journal Nature, and you can hear from some of the researchers involved in the video below.

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