The nearly 100 million-year-old Argentine specimen shows hind legs and a jugal cheekbone, with micro-CT scans revealing skull details including nerves, blood vessels and buried bones.
Researchers said the find supports early snakes as larger, wide-mouthed predators rather than small burrowers, and shows hindlimbs persisted long before mostly limbless modern snakes emerged.
Published in Science Advances in 2019, the fossil remains a key transitional example despite later studies from Brazil, brain reconstructions and a 2025 Scottish squamate adding complexity to snake evolution.
How is new technology revealing that snake ancestors were more lizard-like than we ever imagined?
With fossils of both predators and burrowers, what was the true origin story of the first snakes?
Why did ancient snakes with legs evolve into the limbless predators of today, and what was lost?