An extremely well-preserved fossil discovered in Argentina is helping scientists understand how snakes evolved. The specimen belongs to Najash Lionegrinaan ancient hindlimb snake that lived about 100 million years ago. Their skulls show that these early snakes still had cheekbones, also called zygomatic bones, but this feature has almost completely disappeared in modern snakes. A 2019 study adds an important piece to a fossil record that has long been too sparse to clearly explain the early stages of snake evolution.
The discovery also called into question common old ideas about the origin of snakes. Instead of starting out as a small hole digger, Najash This indicates that the ancestors of modern snakes were animals with large bodies and wide mouths. The fossils also showed that early snakes were grasping on their hind legs for a long time, before the emergence of today’s mostly limbless snakes.
“This supports the idea that the ancestors of modern snakes had large bodies and large mouths, rather than small burrowing forms as previously thought,” explained Fernando Galberoglio, of the Azara Foundation, Maimonides University, Buenos Aires, Argentina. “This study also reveals that early snakes retained their hindlimbs for long periods of time, before the emergence of modern snakes, which are largely completely limbless.”
Details of skull hidden inside 100 million year old fossil
The fossil snakes reported in the study lived in northern Patagonia and are closely linked to ancient southern lineages that lived in Gondwana. Researchers say the group appears to be related only to a small number of rare snakes that still exist. To see inside the specimen without damaging it, the research team used micro-computed tomography (micro-CT) scans. This allowed them to reconstruct the skull in great detail, including nerve and blood vessel routes and bones buried in the rock.
This level of detail helped resolve a long-standing anatomical debate. For generations, scientists have misunderstood the cheekbones of snakes and their snake relatives. Najash The fossils gave them direct evidence to correct the record. The study’s authors claimed that these new skulls and skeletons revealed the sequence of bone loss that ultimately produced the highly specialized skulls of modern snakes.
“This study revolutionizes our understanding of the cheekbones of snakes and non-snake lizards,” said Michael Caldwell, professor in the Department of Biological Sciences and Earth and Atmospheric Sciences and co-author of the study. “After being misunderstood for 160 years, this paper corrects this very important feature based on empirical evidence rather than speculation.”
“This study is important for understanding the evolution of modern and ancient snake skulls,” Caldwell added.
The paper, “New skull and skeleton of the Cretaceous legged snake Najash and the evolution of body plan in modern snakes,” scientific progress In 2019.
Later research added a further twist to the snake’s origin story
Research published since 2019 Najash The paper made the story even more interesting. In 2020, paleontologists said: Boipeba tayasuensisa Late Cretaceous blind snake from Brazil. The fossil pushes the record of blind snakes deeper into the age of the dinosaurs, suggesting that some of the earliest blind snakes were much larger than their living relatives, reaching over a meter in length. The discovery supports the idea that part of the early evolution of Gondwanan snakes was more diverse and often larger than previously thought.
And in 2023, again scientific progress This study approached the origin of snakes from a completely different angle by reconstructing the brains of living squamates and fossil snakes. The study suggests that the ancestors of crown snakes, the group that produced living snakes, may have adapted to burrowing but also acted opportunistically. Rather than neatly resolving the debate, the results showed that the origins of snakes are likely complex, and that different branches of the snake family tree may preserve different clues about how body shape, habitat, and feeding styles evolved.
2025 nature This study adds further context by describing a Middle Jurassic squamate from Scotland that has an impressive combination of lizard-like and snake-like features. The authors found that early squamate evolution involved a great deal of anatomical experimentation and convergent evolution, which helps explain why the story of the earliest snakes has been so difficult to unravel from fossils alone.
why Najash still important
Despite subsequent discoveries, Najash It’s one of the clearest windows into key stages of snake evolution. This photo captures a moment when the snake still had its hind legs, retained a skull resembling a lizard in some respects, and had not yet fully acquired the body plan seen in its modern descendants. It is this combination that makes fossils so valuable. It not only shows ancient snakes. It depicts the evolution of ancient snakes.
The University of Alberta described this initiative as part of the Faculty of Science’s broader mission as a leading center for research and education, focused on advancing knowledge through classroom, laboratory, and field research.
