As the quest to understand our present has us piecing together as many parts of the past as we can find, a new fossil emerged of an ancient snake with legs.
And just as the paleontologists who dug it up hoped, this fossil illustrated one of our planet’s many incredible stories of its ever-evolving species.
For a long time, researchers have been sitting on certain questions about snakes – such as their origins, and how they lost their legs and limbs. Although there was relative certainty that snakes had evolved from their limbed fellow lizard reptiles, and aquatic snakes were already known to have limbs, this fossil from Argentina’s Río Negro Province was the missing evidence that they were waiting for of land snakes with a history of limbs.
In fact, they had the rear-limbed body of this specimen, and suspected it was a snake. But its quintessential snake skull was the only way they could be certain.
Snake skulls provide the species with their unique ability to both capture and consume food without limbs, which enabled them to survive without them in the first place. But for a long time now, it was hypothesized that snakes had evolved from small, worm-like burrowing lizards, and that their skulls grew to compensate for their dietary survival. But a bone (called the jugal) which was found in this old fossil skull with not one but two of the same parts as its lizard ancestors, linking it to both lizards and to modern-day snakes which retain only one part, prove otherwise.
Their skulls were, in fact, large first – like lizards – and because of the predatory advantage it gave them, their bodies were able to shrink around it. Essentially, we can see from Najash is that snakes were evolving towards the skull mobility necessary to ingest larger prey items – the landmark feature of most modern snakes.
Unlike the marine snake fossils, this specimen was not flattened by the weight of overlying sediments as it would have been in water, but was amazingly preserved in three dimensions.