How is a snake not the same as a legless lizard?

Question

Rather than have a 10 hour argument with some faceless online person, I decided I'd rather ask someone who knows. Then I can follow up with their answer and know whether I'm right or he is.
I saw a photo of a legless lizard and I see no difference between it and a snake. So how do the scientists who study these things know the difference?
I don't think the lizard or snake tells them "Hey I'm a lizard, not a snake."

Answer 1

The common ancestor of all snakes is indeed a lizard. So, technically, all snakes are descendants of a legless lizard. Snakes used to be classified in a different order than the lizards, but now practically all scientists have reclassified snakes in the same order as lizards. The new order is known as Squamata. However, snakes are classified in its own suborder, separate from all other lizards. That is because even though leglessness has evolved many different times among the lizards, none of these legless lizards has evolved to the same extent as snakes and none of the legless lizards is particularly close to the snakes phylogenetically.



Although there is some disagreement, many scientists agree with Dr. Lee and Dr. Caldwell that snakes are most closely related to the monitor lizards. Snakes probably evolved in a marine environment, from a marine lizard closely related to the extinct mosasaurs, which are lizards classified in the same family as the living monitor lizards. Because of that, Dr. Michael Lee has found similarities between the eyes of snakes and the eyes of fish. These similarities are due to convergent evolution, or similar adaptations to a similar (in this case aquatic) environment. Most legless lizards, however, still retain eyelids and they evolved on land. Snakes are also quite elongated, much longer than most lizards. Legless lizards also tend to retain at least some of the pelvic bones, but a vast majority of snakes have lost all traces of the pelvic bone. Snakes have also evolved a big mouth that allows most of them to feed on prey that no lizard can handle. The oldest known fossil snakes have this feature, even though these snake fossils still retain tiny hindlimbs. These snakes were also found in marine deposits. Although some snakes have evolved smaller, less mobile jaws, these appear to have evolved as adaptation to insect feeding in underground habitats, in which there is little room to expand the jaws and also little need since insects are easy enough to swallow with small jaws.



Based on these anatomical differences and others, snakes were originally classified as a separate order from the lizards, until more recently available evidence shows that snakes actually are more closely related to lizards than to any other reptilian order, so close in fact that they were combined into a single order. Despite their close relationship, snakes branched off from their lizard ancestor before the extinction of the dinosaurs, and they have evolved a good deal of new features not found in any legless lizards. For these reasons, snakes are placed in a suborder of their own, and not regarded as just legless lizards.

Answer 2

The thing is that animals are not classified by how they look.

Snakes and legless lizards look pretty much the same if you don't get to examine them properly, but think about it. When classifying animals, you don't classify them by how much the animals have in common. Let's take a journey to good ol' wikipedia and their page on tenrecs.

http://en.wikipedia.org/wiki/Tenrecidae

The tailless tenrec looks a lot like a shrew. The lesser and greater hedgehog tenrec looks like a hedgehog. The lowland streaked tenrec looks like someone went a bit crazy with the cloning machine and accidentally left a lion, a hedgehog, a zebra mouse, and some bright paint in there. (I mean, c'mon. Whoever designed that thing must have been taking some pretty funky stuff) But they're all in the same family, because if scientists have got it right, they all had the same ancestor which animals which are not in their family did not have.



So snakes and lizards all had the same ancestor, right? But they branched off. After that, they can't really 'branch on' again. A lizard which evolves to live without legs does not suddenly go back to becoming a snake. I've been told that if you want to 'register' a new animal, you often have to collect a specimen and get it's DNA sent off. Then it can be classified and put it it's family. Classifying animals has more to do with genetics than appearances. However, as has already been covered, lizards do have a number of traits which snakes do not. So if you don't happen to be a very clever person with a lab, just wait to see if it blinks. If it does, it's a lizard. That's probably the easiest thing to do.



I'm sorry if I did not understand your question properly - I wasn't sure if you were asking why a legless lizard is considered a lizard if it looks like a snake or how scientists know that a legless lizard is a lizard. (try saying that 10 times over really fast...)

Answer 3

It has to do with evolutionary history. Snakes and lizards both evolved from a common ancestor, an animal that probably a lot like a lizard. However, many lizards lost their legs again. They are not related to snakes at all. This is a phenomenon called Convergent evolution, also called homoplasy. This is when two organisms which are not closely related evolve similar features because they are trying to solve the same problem. The reason snakes are not legless lizards is because snakes and legless lizards are not very closely related, even though they have similar features. Just like how bats are not the same a birds even though they both have evolved the ability to fly.

Answer 4

Well, without genetic testing which would show them to be lizards rather than snakes there are some differences.

Legless lizards have eyelids, snakes do not. Lizards have external ear holes, while snakes do not. The lizards have very long tails and a normal sized body. A snake has a very long body and a short tail.

edit: also, snakes have very distinct tongues with smelling organs on them while legless lizards have more "normal" fleshy tongues.

Answer 5

I see their are already some very best and distinct solutions right here and that i agree with each of them. Nonetheless I ought to respond to the trendy reply in regards to the myth and the detaching legs. A real scientist makes observations and creates a conclusion headquartered on those observations. Religious scientists out with a conclusion and try to help it with tips and observations. Its working backwards! Here's an illustration: we could say i have a glass of water, 1/2 full. You see water droplets on the aspect of the glass and conclude that the glass was once full at one time. Do you quite have any thought of how the glass came to be half empty established on that knowledge? Science is not about guessing, I would count on that a giraffe came to visit and needed a drink. Which may be real (nonetheless not going) however you are not able to take it as a truth without any proof to support it. Simply figuring out that snakes had legs at one time isn't adequate expertise to make any conclusions on how they lost them.