- Snakes are limbless, scaly vertebrates with over 4,000 species on every continent except Antarctica.
- The key evolutionary question is why snakes lost their limbs, with three main hypotheses: aquatic, terrestrial, or burrowing origins.
- A new fossil, Tametara mirim (80 million years old from Brazil), is the best-preserved early snake, showing traits of a head-first burrower.
- Brain cavity reconstruction reveals reduced visual centers and simplified forebrain, supporting a subterranean lifestyle.
- In contrast, the early snake Dinilysia from Argentina had surface-dwelling adaptations, indicating early snakes already diversified in habitat.
- The study reframes the debate: snake origins are not a single environment but a complex, branching evolutionary path.