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Meet Legged Snakes and How They Differ From Lizards

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key point:

  • The discovery of a 95-million-year-old fossil has changed scientists' understanding of when snakes evolved to lose their legs and how big snakes in the middle were.
  • Traces of the lost legs still exist in the form of vestigial organs in some snake species, such as pythons and pythons.
  • There are legless lizards, which have characteristics that distinguish them from snakes.

Snakes have long been believed to be associated with the lack of legs. In fact, it's one of the primary ways scientists identify snakes today! Still, there are many mysteries surrounding the origin of snakes and what caused them to lose their limbs. In recent research, a lot has come out about snakes and when they had legs! Today we're going to explore some of the science behind snakes, their legs, and some very strange intermediate creatures that don't quite fit our current mold. Let's meet a snake with legs and how it differs from a lizard!

ancient legged snake

How is it different to meet a snake with legs and a lizard?
Recent fossil discoveries have had an incredible impact on the way scientists understand ancient snakes and their legs.

©gabor_szikora/Shutterstock.com

Snakes have existed in their familiar form for about 100 million years. Since then, humans have used a number of identifying factors to help classify them into their respective taxonomic sections (scientific categories). More recently, however, scientific discoveries have allowed us to peer into the past and see some ancient people. In some of these fossils, the snakes had legs!

During excavations in the La Buitrera paleontological zone in Argentina's Río Negro province, a fossil site was discovered containing multiple fossils of ancient snakes. These fossils are from about 95 million years ago and show us some incredible changes that were going on in reptiles at that time.

In that fossil, there was one specific specimen, a snake now named Nagash rionegrina (Hebrew for snake). What makes Nagash so interesting to scientists is that it was the first terrestrial snake to have strong hind legs. Before this discovery, only older aquatic specimens had been found with hind legs.

How Nagash rionegrina turned modern snake theory on its head

Meet Legged Snakes and How They Differ From Lizards
Many theories suggest that small, burrowing lizards were the ancestors of modern snakes.

© Creeping Stuff/Shutterstock.com

Although Nagash rionegrina has allowed scientists to look back millions of years into the past, the full picture remains unclear. Still, it gave us some important information; namely, it shattered previously held theories about the origin of modern snake species.

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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 the modern snakes we understand today. The most primitive examples of these "burrowing snakes" resembled scorpionids alive today. ( See picture above!)

However, the snakes found at the dig site looked nothing like their small, cave-dwelling ancestors. Instead, they had massive skulls, sharp teeth, and massive bodies, meaning the ancient ancestors weren't small burrowing lizards at all.

"Our results support the idea that the ancestors of modern snakes were large, with large mouths, rather than the small, burrowing forms previously thought,"

Fernando Gaberolio

Why do snakes lose their legs?

Meet Legged Snakes and How They Differ From Lizards
Snakes lost their legs due to the combined evolutionary pressure of swimming and hunting in burrows.

© Charles Baker / CC BY-SA 4.0 – License

As we learn more about ancient snakes, the ancient history of snakes has become clearer. Still, there are areas that are currently unknown. One of the toughest questions scientists face is why snakes lose their legs. Thanks to fossil dig sites, we know where they came from (large lizards similar to modern Komodo dragons), but why did they lose their legs?

Current theories suggest that two main evolutionary pressures are responsible for the leglessness of modern snakes. The first stress is the increased hunting ability of legless snakes. Even today, many snakes hunt in burrows and small enclosed areas. For snakes that hunt small creatures that hide in burrows and tight areas, having full mobility in these areas will be a huge hunting advantage. Over time, evolutionary pressure enabled these highly maneuverable and agile reptiles to outperform their less mobile legged counterparts.

The second stress is about swimming. The ancient ancestors of snakes spent a long time in aquatic environments, and many species today continue in the same vein. Legs aren't particularly useful in water, especially when a long, lithe body is better suited for speed and maneuverability in water.

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While this may be only part of the answer, these two selection pressures likely contributed to the snake losing its legs.

Do snakes have legs today?

Meet Legged Snakes and How They Differ From Lizards
Some python and boa constrictor species have lower leg stumps, which are rarely used today.

©Michelle Marks/Shutterstock.com

There are thousands of species of snakes and lizards on Earth. In this range, are there any legged snakes alive today? Well, in short, no. Snakes lost their functional legs millions of years ago, most likely around the time our fossil friend Nagash rionegrina roamed the Earth.

Even so, some snakes still have leg remnants to this day. The most famous are pythons and boa constrictors. In most boa constrictor and boa constrictor species, there are vestigial organs that are clearly remnants of legs, just near the base of their bodies. These "legs" don't serve much purpose other than to provide some extra "grip" while mating.

What Legless Lizards Are There?

Meet Legged Snakes and How They Differ From Lizards
There are many species of legless lizards that are quite different from snakes.

© Dr. MYM/Shutterstock.com

While no modern snake has legs, several species of lizards do not. Currently, there are eight families of legless lizards, each with dozens of species (some exceeding 1,500 species). They live in Eurasia, Southern Europe, North America, Australia and Africa.

One of the most famous groups of legless lizards is the lizard family, also known as skinks. There are 1,500 species of skinks, many of which have no limbs at all.

These groups of limbless lizards show that evolution is not a single change from one species to another, but a slow and gradual creep, often with the previous species still 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 main factors that help scientists classify them apart. Legless lizards usually have:

  • stump
  • eyelid
  • Outer ear or ear hole
  • Lack of broad ventral scales
  • Notched tongue (as opposed to a snake's forked tongue)
  • Long tail (snakes have short tails and long bodies)
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Comparing skinks to other lizards

Smallest Lizard - Brown Skink
Brown skinks have short legs, no necks, and smooth skin. Its tail and body are more snake-like.

©Stock Anole/Shutterstock.com

Have you ever observed the difference between a cute little green lizard and a brown or black skink in your garden? Skinks are definitely more easily startled and more snake-like! They have shorter legs, no necks, and just look more like snakes! Unlike snakes, they can run around at speeds of up to 60mph – so those little legs really come in handy!

Other lizards, such as the green chameleon, are curious and friendly. They may check on you and wait until they feel threatened before running away. They might not be as fast as their skink cousins — but they might be better at climbing. Are lizards like green chameleons more evolved than their skink relatives? Evolution of a species takes a lot of time – this could be an opportunity to see both subspecies evolve at their own pace right in your backyard!

Green Anole Lizard Relaxing
Green Anoles look more like lizards, with long legs and toes, a pronounced neck, and scaly skin.

© Brad Boland/Shutterstock.com

'Monster' snake 5 times bigger than a boa constrictor discovered

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snake with legs

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about the author

Colby Maxwell


Colby is a freelance writer from Charlotte, North Carolina. When he's not distracted by the backyard bird feeder, you can find him camping, exploring, and telling everyone around him what he's learned recently. There's a whole world to learn, and Colby is content to spend his life learning as much of it as he can!

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