Paleontologists have discovered an exceptionally well-preserved snake fossil in Brazil, reshaping our understanding of early snake lifestyles and complicating the long-standing debate regarding their ancestors—did they burrow underground, swim in oceans, or crawl on the surface?

Co-author Dr. Roy Ebell, a researcher at Museums Victoria Research Institute, stated, “Snakes are essentially highly modified lizards.”

He noted, “At some point during the dinosaur era, one lineage of lizards lost their limbs and elongated their bodies. The critical question is why?”

Dr. Ebell further explained, “Various theories have coexisted for over a century.”

Some scientists propose that early snakes adapted to aquatic environments with long, limbless bodies, similar to eels. Others believe they thrived on the surface among fallen leaves, while a third theory suggests they became adapted to a burrowing lifestyle, similar to modern blind snakes.

However, the debate is hindered by limited fossil evidence, with fewer than ten early snake skeletons identified from that era.

In their study, Dr. Ebell and colleagues analyzed the exceptionally preserved skull and post-cranial material of a new species of stem snake known as Tametaramirimu, which inhabited what is now Brazil during the Late Cretaceous period, approximately 85 to 75 million years ago.

This fossil, unearthed in 2020 near Presidente Prudente in São Paulo state, marks the first articulated snake fossil ever found in Brazil and one of the few three-dimensionally preserved Mesozoic snake fossils globally.

What sets Tametaramirimu apart are the extraordinary details preserved in its skull.

Paleontologists employed high-resolution CT scans to reconstruct the brain, cranial nerves, and inner ear with unprecedented detail, producing the most comprehensive picture of early snake brain anatomy to date.

These reconstructions reveal a brain structure distinct from both other early snakes and modern snakes, suggesting significant evolutionary changes in brain form and possibly sensory capabilities.

Dr. Ebell and his team correlated brain data with fossil bone microstructure analysis, which indicates an animal’s lifestyle through skeletal density and thickness.

Both lines of evidence lead to the same conclusion: Tametaramirimu was adapted for burrowing.

Dr. Ebell stated, “Burrowing animals develop denser, thicker skull bones, particularly in the skull roof.”

This adaptation likely reinforces the skull against stresses incurred during burrowing.

Tametaramirimu displays these characteristics, classifying it among the most specialized burrowing reptiles today, far removed from lizards and snakes with more common lifestyles.

Furthermore, the study’s evidence extended beyond the skull shape.

The researchers digitally reconstructed the brain cavity, achieving the most detailed visualization of an early snake brain yet.

They believe this layout closely resembles brain shapes of living burrowing species, marked by a reduced visual center and simplified forebrain indicating an underground lifestyle.

Holotype of Tametaramirim. Image credit: Simões et al., doi: 10.1038/s41586-026-10809-9.

The findings sharply contrast previous research on Dinilisia patagonica, an Argentinian snake known for its non-burrowing, surface-dwelling nature.

These comparisons suggest that early serpentine lineages were not uniform; instead, snakes appeared to diversify early into burrowing, terrestrial, and even marine adaptations, developing distinct lifestyles over tens of millions of years.

Dr. Ebell highlighted, “The two oldest snakes studied show even greater brain differences than most contemporary snake lineages.”

Dinilisia patagonica existed on the surface, while Tametaramirimu had vision adapted for a life spent in the dark.

This significant discovery contributes to the growing repository of well-preserved Cretaceous snake fossils, helping paleontologists unravel the complex puzzle of how lizard-like ancestors evolved into the diverse range of over 4,200 extant snake species today.

“Our results provide quantitative, multi-faceted confirmation of the fossilizability of stem snakes and address a long-standing debate previously reliant on qualitative assessments and isolated anatomical evidence,” the researchers concluded.

“More broadly, these findings illustrate that the origin of snakes was influenced by multiple ecological pathways, highlighting the diverse evolutionary adaptations that facilitated one of the most drastic changes in vertebrate body plans.”

The complete research paper can be found here, published in the journal Nature on July 22, 2026.

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TR Simões et al. Extraordinary brain and ecological diversity in early snakes. Nature published online on July 22, 2025. doi: 10.1038/s41586-026-10809-9