A fossil reptile almost 240-million-years old has been found in the Italian Alps has changed our understanding of the evolution of lizards and snakes.

Megachirella wachtleri has features unique to squamates, the group including lizards, snakes and legless lizards that look like worms. Squamate evolution began on the supercontinent of Pangaea.

Her existence helps explain the transition from more primitive reptiles to the large, diverse order that now slithers, creeps and burrows across every continent except Antarctica.

“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,” co-author Michael Caldwell from the University of Alberta said in a statement.

“It’s almost a virtual Rosetta stone,” said Caldwell.

Scientists used a new X-ray technology to examine parts of the fossil embedded within the rock to determine the species was in fact part of the lizard family based on head, shoulder and wrist features.

Since this discovery, scientists didn’t know much about the early stages of lizard and snake evolution. Lizard fossils are hard to come by, considering the fragile nature of their skeletons.

Before Megachirella, the oldest-known squamate fossils were bits of jaws belonging to lizards and snakes found in the United Kingdom, Morocco and Central Asia.

“Our results re-shape the diapsid phylogeny and present evidence that M. wachtleri is the oldest known stem squamate,” the study reads. “Megachirella is 75 million years older than the previously known oldest squamate fossils, partially filling the fossil gap in the origin of lizards, and indicates a more gradual acquisition of squamatan features in diapsid evolution than previously thought.”

The researchers also noted that for the first time, “orphological and molecular data are in agreement regarding early squamate evolution, with geckoes—and not iguanians—as the earliest crown clade squamates.”