Scientists just discovered an ancient fossil known as the “mother of all lizards,” or: the oldest ancestor of squamates, a category of reptiles that include snakes, lizards and creepy legless worms called amphisbaenians, which make up the largest group of living land vertebrates on Earth. Despite occupying so much of the Earth, scientists have found gaps in its understanding of squamate lineage.
Genetic evidence suggests that squamates evolved in the Permian period, over 250 million years ago. But the previous oldest squamate fossil discovered was only about 180 million years old. “That's more time than there is between us and the dinosaurs, and we had no clue what was going on,” Tiago Simões, a paleontologist at the University of Alberta, told the . The discovery of the latest ancient fossil might help fill that gap.
The 3-inch fossil preserved the form of a Megachirella wachtler, a lizard that lived during the middle Triassic period, 240 million years ago. Back then, flowers had not yet developed, and the world’s land was clumped together in a supercontinent called Pangaea. The fossil was found in marine sediment, surrounded by fossilized land plants, which suggests that she might have been swept out to sea during a powerful coastline.
An amateur fossil hunter discovered a part of her skeletons in the mountains of northern Italy, and scientists first described it in 2003. Now, high-resolution micro CT scans has allowed researchers to investigate the fossil’s origins, identifying features that are unique to lizards, and some ancient traits that modern squamates have lost: a small cheek bone called the quadratojugal, belly bones called gastralia that are also found in many dinosaurs.
Co-author of the paper on the discovery, Michael Caldwell, called the fossil a “virtual Rosetta stone in terms of the information that it gives us on the evolution of snakes and lizards.” She could help link the evolution of primitive reptiles to the crawling, slithering reptiles that live on Earth today.