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What's the difference between a legless lizard and a snake? Jessi breaks it down: ears, eyelids, tongue, legs, tail, and jaw bones. Featuring a sand boa and a European legless lizard (aka glass lizard, or sheltopusik).

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Hi, I'm Jessi, this is Leonard, and this is Sandy.  We're from Animal Wonders and only one of us is a snake.  

(Intro)

Animal Wonders is a non-profit organization that rescues displaced and non-releasable animals.  We provide them a lifelong home and allow them to become ambassadors for their species by giving educational presentations in schools and at other public events. 

When most people look at these two animals, they see very similar reptiles and they guess they're both snakes, which is understandable.  They're both long, scaly, and have no legs, but Leonard here is actually not a snake.  He's a lizard--a legless lizard.  I know some of you might be saying, but Jessi, isn't a legless lizard just a snake?  Aren't they the same thing?  And to that, I say, no, so let's figure out why.

In order to really understand why they aren't the same, we have to take a closer look at what makes a snake different from a lizard.  If you ignore their bodies for a second and just look at their faces, you can see some differences right off.  Their eyes look different.  Sandy looks pretty alert while Leonard looks almost grumpy.  That's because Leonard has movable eyelids and Sandy doesn't.  Also, if you follow their lips back to where their cheeks would be, you can see a small hole on Leonard and no hole on Sandy.  That hole on Leonard is his ear.  Lizards have external ears and snakes don't.

Now, let's take a step back and look at their bodies.  Sandy has a very flexible body and if I turn her over, I can find where her tail starts.  It's way back here.  It's really short.  I can tell where it starts because I can see her (?~1:46), or the place where she gets rid of her leftovers or I could just say, this is where she poops.  Leonard, on the other hand, when I pick him up, his body is much firmer and much less flexible.  To find where his tail starts, I just look for his (?~2:02).  It's right here and it's in a much different place than snake.  Leonard's tail is about the same length as his body.  So those are some pretty good differences that you can see from the outside.

I'm going to go ahead and put him back.  There you go, buddy.  They are definitely different kinds of animals, but let's delve in a little deeper?  Lizards and snakes are both reptiles in the order Squamata, which means they have scales that overlap and have more movable quadrate bones, which is part of their jaw.  Squamates have flexible jaws because their quadrate bone is movable, which makes their mouth open quite wide.   As a result, they can swallow prey whole.

Lizards are thought to have originated in the late Triassic period and quickly diversified.  Fossil records show that there were more modern-day lizards in the mid-Jurassic.  Some lizards grew huge while others burrowed and evolved to have smaller and smaller limbs and eventually, they lost them altogether.  Now, let's talk about snakes.  Scientists who specialize in studying ancient snakes and their evolution have found fossils that date back to 150 million years ago, which is the late Jurassic.  It's difficult to get a good idea of exactly when they came onto the scene because their fossils are small and fragile, but scientists agree that snakes evolved from four legged lizards.

Snakes evolved many new and interesting adaptations, including an even more flexible jaw.  Their quadrate bone became elongated so they could open it even further and their mandibles, these bones right here, aren't fused together, so they can move independently.  So snakes can literally stretch their jaw open like this and then stretch it apart like that to fit something larger than their head into their mouth.

Another way we can tell that snakes evolved from lizards is because we can see remnants of their four-legged lizard ancestors in some modern-day snake species.  Boas and pythons have retained vestigial legs.  Vestigial means a very small remnant of something that was much larger.  If you look closely at a male boa, you can see that they have small claws or vestigial femur bones on either side of their (?~4:01).  Sandy is not a good example because she's a female and theirs aren't as distinct.  If you were to look at her skeleton, you would see a vestigial pelvic bone that doesn't attach to the backbone.  It just kind of floats in the muscle, which is just another callback to their ancient lizard ancestors.  

There are many species of snakes that have completely lost their vestigial legs and there are many legless lizard species that have retained their vestigial legs, so while there are many big differences between these two, they are both still in the process of evolving, and they have many similar adaptations, which is an example of convergent evolution, and here's two more things that make legless lizards different from snakes.

Snakes have forked tongues and legless lizards don't.  Some lizard species have a forked tongue because this adaptation evolved separately, but no legless lizard species have that special forked tongue, and the last big difference between these two is that Leonard the legless lizard has the amazing adaptation of being able to drop his tail and regenerate it.  Legless lizards are sometimes called glass lizards, and that's because when they're threatened and a predator grabs ahold of their tail, they do this amazing rolling movement, twisting their bodies in a circle.  That movement will put a lot of pressure on their tail if it's held by the predator, and that pressure will end up breaking the tail off, sometimes breaking into many pieces resembling glass shattering.  These pieces of tail will immediately start wiggling around and the legless lizard will escape with his life while the predator is distracted by the chaos of tail wigglings going on.

So the next time you see a long, scaly animal and immediately think snake, maybe take a moment to acknowledge that it might also be a legless lizard and now you'll know how to tell the difference.  Thanks for watching.  I hope you enjoyed learning about why legless lizards are not snakes.  If you'd like to go on some more adventures with us and learn more about animals, subscribe to our YouTube channel, AnimalWondersMontana and from Leonard, Sandy, and I, thanks for watching.

(Endscreen/Credits)