The ancient snake with legs
Snakes have been around in their familiar form for about 100 million years. From then on, there have been a few identifying factors that humans have used to help categorize them into their respective taxonomical sections (scientific categories). Recently, however, scientific findings have allowed us to peer into the past and see some ancient individuals. In some of these fossils, the snakes still had their legs! During a dig in the La Buitrera Paleontological Area within Argentina’s Río Negro province, a fossil site was found that contained multiple fossils of ancient snakes. The fossils were from around 95 million years ago and show us some incredible changes that were taking place among the reptiles of the time. Within that fossil site was one particular specimen, a species of snake now named Nagash rionegrina (Hebrew word for snake). What made Nagash so interesting to scientists was that it was the first example of a terrestrial snake species that had robust hind legs. Before this find, only older and aquatic-dwelling specimens had been found with hind legs.
How did Nagash rionegrina shake up modern snake theories?
Although Nagash rionegrina has allowed scientists to look millions of years into the past, the full picture still isn’t clear. Still, it gave us some vital information; namely, it crushed the previously held theory of the origin of modern snake species. Before Nagash rionegrina, one of the most commonly held theories was that snakes evolved from blind, burrowing lizards that lived hundreds of millions of years ago. Slowly, they lost their legs and developed into what we understand today as modern snakes. The most primitive examples of these “burrowing snakes” are similar to the ones alive today from the scolecophidian order. (See picture above!) The snakes found at the dig site, however, didn’t resemble small, burrowing ancestors at all. Instead, they had large skulls, sharp teeth, and large bodies, meaning that the ancient ancestors weren’t small burrowing lizards at all.
Why did snakes lose their legs?
With our understanding of ancient snakes broadened, the ancient history of snakes has become a bit clearer. Still, there are some areas that are currently unknown. One of the most nagging questions scientists face is exactly why snakes lost their legs. Thanks to the fossil dig site, we know where they came from (large-bodied lizards similar to modern-day komodo dragons), but why did they lose their legs? The current theories hold that two main evolutionary pressures are responsible for the lack of legs in modern-day snakes. The first pressure was the increased hunting ability that a legless snake would have. Even today, many snakes hunt in burrows and small, confined areas. For a snake hunting small creatures that hide in burrows and tight areas, having total mobility in those areas would have been a massive hunting advantage. Over time, evolutionary pressure allowed these highly mobile and flexible reptiles to edge out the less mobile ones with legs. The second pressure is in regards to swimming. Ancient ancestors to snakes spent a lot of time in aquatic environments, with many species today continuing in the same vein. Legs aren’t particularly useful in the water, especially when a long, lithe body is better suited for speed and maneuverability in the water. While this is likely only a part of the answer, these two selection pressures most likely contributed to how snakes lost their legs.
Do any snakes today have legs?
There are thousands of species of snakes and lizards across the earth. Within that range, are there any snakes alive today that have legs? Well, in short, no. Snakes lost functional legs millions of years ago, likely around the time that our fossil friend Nagash rionegrina was roaming the earth. Still, there are some species of snake that have the remnants of legs, even to this day. Most notably, pythons and boas. In most python and boa species, there are vestigial organs that are clearly the ancient remains of legs, right near the bottom of their bodies. These “legs” aren’t used for much else besides giving some extra “grip” when they are mating.
What kinds of legless lizards are there?
Although there aren’t any modern-day snakes with legs, there are a few species of lizards that don’t have any legs. Currently, there are 8 families of legless lizards, each with dozens of their own species (with some having over 1,500). They live in Eurasia, Southern Europe, North America, Australia, and Africa. One of the most famous groups of legless lizards is Scincidae, otherwise known as skinks. There are 1,500 species of skinks, many of which have no limbs at all. These groups of limbless lizards show how evolution isn’t a single change from one species to another, but a slow and gradual creep, often with the previous species still being around!
What is the difference between a legless lizard and a snake?
Although it may not look like it, legless lizards and snakes are different groups of animals. Here are some of the primary factors that help scientists classify them separately. Legless lizards usually have:
vestigial limbseyelidsexternal ears or earholeslack of broad belly scalesnotched tongues (as opposed to snakes’ forked tongues)long tails (where snakes have short tails and long bodies)
Up Next…
We think lizards and snakes are some of the coolest, strangest creatures in the animal kingdom. So we’ve curated tons of posts for those who can’t get enough of these crazy reptiles! The World’s 10 Largest Lizards– An iguana that can stay underwater for 30 minutes? A 300-pound venomous, man-eating monster? Learn about ten titan lizards, from neat to nightmare fuel. Discover the 10 Weirdest Snakes in the World– If you think a snake with legs or a legless lizard is weird, you won’t believe how freakish these specimens can be! 7 Snakes that are Longer than a Komodo Dragon– Sure, a ten-foot death lizard is horrifying. But so is the snake that can swallow a person whole…
