The ancient snake Najash challenges everything we thought we knew about how snakes evolved

Nature · Published 3 October 2026 Swipe more like this →

In short: For decades, scientists believed snakes descended from tiny, burrowing lizards. But the discovery of Najash rionegrina, a 95-million-year-old fossil from Argentina, tells a different story. This legged predator possessed a large mouth and a distinct cheekbone, proving that early snakes were far more diverse and robust than previously assumed.

The 2019 analysis of Najash rionegrina fossils, unearthed in Argentina’s La Buitrera Paleontological Area, has fundamentally altered the scientific understanding of snake origins. By using micro-computed tomography (micro-CT) to scan three-dimensional, uncrushed skulls, researchers corrected a 160-year-old misconception regarding the jugal bone. While modern snakes have almost entirely lost this cheekbone, Najash retained it, providing empirical evidence that clarifies the sequence of bone loss in the evolution of the modern snake body plan.

These findings directly challenge the long-held theory that snakes originated from small, blind, burrowing lizards. Instead, the evidence suggests that the ancestors of modern snakes were large-bodied, wide-mouthed predators, more akin to lizards like the Komodo dragon. Najash lived nearly 100 million years ago, a period when it still possessed robust hindlimbs. This indicates that snakes held onto their legs for an extended duration—long after they had likely lost their forelimbs, which researchers estimate occurred around 170 million years ago.

The evolutionary history of snakes remains complex, with recent studies highlighting significant anatomical experimentation. While 2020 research on the blind snake Boipeba tayasuensis and 2023 brain reconstructions suggest that some early lineages may have been adapted for burrowing, Najash remains a critical window into this transition. It captures a moment when snakes were neither fully lizard-like nor fully modern, serving as a vital link in the vertebrate story of how body shape, habitat, and feeding styles evolved over millions of years.

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