When Snakes Had Legs...

Dec 3, 2019 By Lauren T, Writer
Lauren T's picture

What’s your reaction when you see a snake? Fear? Revulsion? Wonder?

Whatever your reaction, we can all agree that snakes are scaly, legless reptiles that slither along the ground. That’s what snakes are, after all.

Snakes in prehistoric times, however, are a very different story. Scientists know that snakes once had limbs, but evolved over time to become the legless creatures they are today. However, there weren't enough fossil records of prehistoric snakes to prove that—until now.

Researchers in the La Buitrera Palaeontological Area of northern Patagonia, Argentina recently discovered new fossils of an ancient snake. These fossils, nearly 100 million years old, include eight skulls, and suggest early snakes had hind limbs for an extended period of time. 

Tracing The Origin

Scientists have long known that lizards, snakes, and a legless worm-like creature known as amphisbaenians shared a common reptilian ancestor. 

Over time, the prehistoric lizards started losing their limbs and evolved into snakes. However, complete fossils of snakes are hard to find because their vertebrae are fragile and do not preserve well.

In 2006, researchers in the northern Patagonia region of Argentina, South America discovered fragments of a terrestrial snake with hind legs. They named it Najash rionegrina, after the limbed biblical snake, Nahash, and the Rio Negro region in Argentina where it was found. 

Najash was a snake/lizard hybrid, the kind that would have been put together by the hands of an evolutionary Dr. Frankenstein! 

With stubby hind legs and a cheekbone (called jugal), Najash bears some resemblance to lizards. And with a large mouth, sharp teeth, and mobile joints, this ancient serpent bears resemblance to snakes. Najash also lacks a series of bony crests in the skull, typical of snakes.

What Does This New Discovery Mean?

This new discovery is especially important because not only is it a well-reserved snake skull, but it also proves several long-held hypotheses about snake evolution wrong.

One such hypothesis assumed that the jugal (cheekbone) is a feature characteristic of all snakes, whether modern or fossilized. MPCA 500, one of the newly discovered and one the best-preserved snake skulls, demonstrates quite the contrary. It is now clear that the jugal as we know it in lizards was present in ancient serpents and disappeared in modern snakes.

Another hypothesis is that snakes evolved from tiny, blind, small-mouthed, worm-like, burrowing lizards. The new Najash fossils also prove this wrong, as shown by their large, sharp-toothed mouths and mobile skull joints. This discovery also proves that snakes lost their front limbs at an earlier time than was assumed, and kept their hind limbs for millions of years!

With the discovery of more Najash fossils, scientists are coming closer to understanding the mysteries of snake evolution. And who knows, perhaps you might discover one!

Sources: Newscientist, NYTimes, Sciencealert, Sciencemag, Smithsonian