Fossil Snake Brains: Tametara mirim

Publication Info:

Transcript:

T.R. Simões et al. Exceptional brain and ecological diversity in the earliest snakes. Nature, published online July 22, 2025; doi: 10.1038/s41586-026-10809-9

Meet Tametara mirim, the newly described fossil snake from Cretaceous Brazil. Living alongside dinosaurs isn't the most impressive thing about this animal, it's how well it's preserved. Paleontologists have been able to reconstruct its brain in such high detail that it's giving clues about why snakes lost their legs!

Episode 316

Notes:

This newly reconstructed Cretaceous brain might finally be solving the mystery about why snakes lost their legs. So, first some background. Snakes are lizards. They're not in an entirely different group of reptiles. They're just a group of lizards that lost their legs. But, don't confuse them with the legless lizards. That's another de-legged group of lizards. Anyway, snakes have been around for a long time, originally showing up in the fossil record back in the Jurassic. But, there's always been kind of a mystery about how and why they lost their legs because, at least from a human pers- pective, it seems like a kind of interesting choice. There have been a lot of ideas to either be better burrowers, or better swimmers, or better at navigating through leaf litter. But, thanks to this newly named species, paleontologists may finally know why. Meet Tametara mirim, the new incredibly well-preserved snake fossil from late Cretaceous Brazil, like 75 to 85 million years ago. It was originally discovered in 2020. And when I say amazingly well-preserved, I mean it because it has most of its postcranial material, which is the material after the head. But, the head is kind of the centerpiece of the find cuz it's so amazingly well-preserved that they were able to reconstruct the shape of the snake's brain. Researchers found that it has reduced visual centers and a simplified forebrain, which is consistent with its secret to being so well-preserved, being extra thick, tough bone on the roof of its skull because it was probably a burrower. That said, the origin of snakes is not as simple as Tametara being a burrower because that is in stark contrast to the reconstructed brain of Dinilysia patagonica from 2015, an even earlier stem snake. It means that snakes diverged and specialized for their different lifestyles extremely early in their evolution. So, you could either say that all the ideas are kind of right, or you could say that the real reason snakes lost their legs was so that they could pretty much do whatever they want. As usual, if you want more information, here's the source.