Early snakes explored life underground, on land and at sea

Snakes are highly modified lizards, with more than 4,000 living species today. The origin of snakes has long been one of evolutionary biology's most debated questions. Their sparse fossil record has made it hard to pin down what drove the evolution of their limbless body plan.

For decades, scientists have argued whether the elongated, limbless snake body first evolved as an adaptation to burrowing or to life in water. A study published in Nature challenges that framing: early snakes did not follow one ecological path but experimented with multiple habitats and sensory strategies.

“Our findings show that early snakes had already achieved remarkable ecological and morphological diversity by the Late Cretaceous, around 80 million years ago,” says lead author Tiago Simões , Assistant Professor at Princeton University.

Brain shapes reveal more than skeletons alone

Researchers describe a new snake species from Late Cretaceous, around 80 million years ago, deposits in southeastern Brazil. The species, Tametara mirim , is one of the best-preserved fossil snake skeletons known anywhere in the world.

The team digitally reconstructed the fossil using computed tomography and cinematic 3D rendering, revealing details of the skull, vertebrae and brain endocast.

Postdoctoral researcher Simone Macrì and Research Director Nicolas Di-Poï , both at University of Helsinki's HiLIFE Helsinki Institute of Life Science , led the reconstruction and comparative analysis of the brain anatomy, linking early neuroanatomy to sensory ecology and habitat evolution.

The researchers compared Tametara with another fossil, Dinilysia patagonica from Argentina.

“The two had strikingly different brain shapes, both from each other and from most other snakes studied. Brain shape and bone microstructure pointed to the same conclusion: Tametara was adapted to burrowing, Dinilysia to life on the ground. Together with evidence from marine sediments, the findings reveal several shifts between burrowing, terrestrial and marine lifestyles in early snake evolution. Different lineages explored different habitats much earlier than previously thought," concludes Research Director Nicolas Di-Poï .

"The brain tells a much richer story than the skeleton alone. By combining computed tomography-based brain reconstructions with data from living snakes, we could show that early snakes were not simply progressing toward one modern condition but experimenting with different sensory and ecological strategies. This means that early snakes did not follow a single evolutionary pathway," says Researcher Simone Macrì.

The study was led by Tiago Simões of Princeton University, with senior authors Nicolas Di-Poï of the University of Helsinki and Annie Hsiou of the University of São Paulo, together with an international team of collaborators.

Tiago R. Simões et al.: Exceptional brain and ecological diversity in the earliest snakes , Nature .

For more information

Research Director Nicolas Di-Poï , nicolas.di-poi@helsinki.fi , tel. +358 2941 59367 (in English or French), University of Helsinki
Postdoctoral researcher Simone Macrì , simone.macri@helsinki.fi , tel. +358 2941 59393 (in English or Italian), University of Helsinki
Assistant Professor Tiago Simões , simoes@princeton.edu , tel. +1- 609-258-2798 , Princeton University