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Deep TimeLife & Evolution

The first snakes

167 million years agoNotableContested

Snakes branch from lizards by the Middle Jurassic: the oldest known fossils, from England, Portugal and the United States, show small, early forms of the group.

The story

Snakes are lizards that lost their limbs, and the oldest known fossils come from the Middle to Late Jurassic. Michael Caldwell and colleagues described Eophis underwoodi from England, about 167 million years old, along with Portugalophis from Portugal and Diablophis from Colorado in 2015. They are tiny and known mostly from jaws and vertebrae, but their features show they are already true early snakes. Earlier work on Parviraptor from England pointed the same way.

How the first snakes lived is debated. One view says they evolved as burrowers in leaf litter and soil, and another that they came from the sea, as lizard relatives such as mosasaurs did later. Cretaceous fossils fill in the picture: Najash from Argentina, about 95 million years old, still had hind legs and lived on land, while Pachyrhachis from the Middle East was marine. The snakes' great spread came after the end-Cretaceous extinction, when mammals and amphibians multiplied as prey.

Why it mattered

  • Snakes are a clear case of how a whole group can lose its limbs and gain new feeding and sensing abilities.
  • Their rise after the asteroid created a vast diversity, today over 3,900 species.
  • The fossils help date the split of snakes from lizards, which genetic clocks alone could not pin down.

Sources

  1. Oldest known snake fossils identified University of Alberta
  2. Remarkable Fossils Push Back Snake Origins by 65 Million Years Scientific American
  3. The dawn of snakes National Geographic
  4. Snake with hips evolved on land, fossil suggests CBC News

Contested history

Consensus: Snakes evolved from lizards by the Middle Jurassic, with the oldest fossils about 167 million years old, but how the first snakes lived is unresolved.

Snakes began as burrowers that lost their legs undergroundDebated
Skull and inner-ear shape in some early forms fit burrowing, though the Jurassic fossils are too incomplete to settle it.
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Snakes began in the sea, like their relatives the mosasaursDebated
Marine Cretaceous snakes such as Pachyrhachis support this, though others place them as later offshoots.
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Tetrapodophis was a four-legged snakeUnsupported
Later study doubted that the specimen was a snake and found its limbs and features better fit a marine lizard.
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