Why is a slow worm NOT a snake?

[Goatboy]

Apologies if this is a daft question.

Wildlife presenters seem to love explaining to us that the Slow Worms are not snakes but are in fact legless lizards. Yet never seem to explain the difference.


So my question is what IS the difference between a legless lizard and a snake. I know lizards have eyelids and snakes don't but surely there are other differences? How do scientists define between the two?

[The Black Rabbit]

Not a daft question at all Goatboy. (Thats the BEST avatar on here by the way).

As far as I was aware, Slow Worms:

Can shed their tails like other lizards when evading predators.(Snakes don't)

They have a partially forked tongue which unlike snakes, cannot protrude out of the mouth.

They are MUCH less flexible in terms of bending their body, than say a Grass Snake or Adder (or Smooth Snake).

Their heads are the same width as their body (or no wider, anyway) (a good method of ID that).

(and the eyelids bit you mentioned).

Does not that help at all?

Doug

[Paul mabbott]

Pygopodidae - Wikipedia, the free encyclopedia
It all goes back a long way in evolutionsry history!

[Goatboy]

That is very helpful Doug, thanks.

I have just read that legless lizards have lost their legs over the centuries through evolution. It would be interesting to know if this happened later than the evolutionary split between snakes and lizards (I'm assuming that they are derived from the same primitive reptiles, may be wrong)

I think I'll doing a bit more research....

[Meta menardi]

This is one of those questions that at first make you go "Doohhhh", then when you think about it, my level of understanding is about "well, because someone told me so".

I think what you want is a cladogram, which shows where things branch, in the way you ask about losing legs and when it happened.

Cladistics - Wikipedia, the free encyclopedia

is a link to the basics of cladistics.

Araneomorphae

is a link to the stuff I am most familiar with, Spiders.

I have not looked for a cladogram for reptiles on TOL (Tree of Life), but it could be there.

Hope this helps or at least provides some interest.

[Ukwildlifeo]

Originally Posted by The Black Rabbit

They have a partially forked tongue which unlike snakes, cannot protrude out of the mouth.

Ive read that too, but look at this:


maybe someone forgot to tell her! I think maybe its that lizards don't protrude there tongue to 'smell the air' like snakes do and somewhere in the literature some wires crossed

[The Black Rabbit]

Originally Posted by Ukwildlifeo

Ive read that too, but look at this:


maybe someone forgot to tell her! I think maybe its that lizards don't protrude there tongue to 'smell the air' like snakes do and somewhere in the literature some wires crossed

Maybe thats true.

And Meta menardi - I thought that God made the Snakes and God made the Slow Worms at the same time - on the "Sixth day" to be precise...

Doug

[Ukwildlifeo]

Originally Posted by The Black Rabbit

Maybe thats true.

And Meta menardi - I thought that God made the Snakes and God made the Slow Worms at the same time - on the "Sixth day" to be precise...

Doug

Dont be silly. Snakes are the work of satan, and slowworms are one of gods creatures.

As for evolution of snakes there were around in the Cretaceous period, so where around with the dinosaurs and evolved from lizards or atleast the same related group. The fossil record is poor though, as snakes ahve small fragile bones.

[Meta menardi]

Originally Posted by Ukwildlifeo

Dont be silly. Snakes are the work of satan, and slowworms are one of gods creatures.

As for evolution of snakes there were around in the Cretaceous period, so where around with the dinosaurs and evolved from lizards or atleast the same related group. The fossil record is poor though, as snakes ahve small fragile bones.

Whoever. Certainly better than I can do. I have to say, having spent quite some time logging snakes (mainly Adders, Grass Snakes seem to be getting very localised), and Slowworms too, I would love to see the Smooth Snake. I will have to move house. Better range of Spiders down South too.

I do love the gold of a slowworm, but the pattern of an Adder is so numinous, it calls to a real memory of pattern in a wild landscape.

[Paul mabbott]

Originally Posted by Meta menardi

........ logging snakes (mainly Adders, Grass Snakes seem to be getting very localised), and Slowworms too, I would love to see the Smooth Snake. I will have to move house. Better range of Spiders down South too. ............

On the other hand wait a few years for enhanced localised global warming and the south may be a desert ... might be a better gamble to sit and wait for the dry heaths to reach you?

[Paul mabbott]

Snakes still have some leg bones although these are obviously non-functional. Clearly their ancestors were legged. This is fascinating suggesting that some early 'snakes' had one pair of functioning legs:
Digimorph - Pachyrhachis problematicus (fossil snake with legs)

Might they have derived from something like the upright lizards? Losing the need for forelimbs and later, retreating under rocks, losing the need for hind ones? Probably leg loss happened several times under different pressures.

[Meta menardi]

Originally Posted by Paul mabbott

On the other hand wait a few years for enhanced localised global warming and the south may be a desert ... might be a better gamble to sit and wait for the dry heaths to reach you?

Paul, you make me nervous, I miss the Avatar. I have always bought houses at the top of hills

1: Because all the cheap secondo cars I bought had a need for some... gravity... in the mornings.

2: Nicer view.

3: Scared of water unless it is outside a Colossal boat and I am inside.

[Goatboy]

This is one of those questions that at first make you go "Doohhhh", then when you think about it, my level of understanding is about "well, because someone told me so".

I was very much aware of that when I started this thread.

Thanks for the heads-up on Cladistics. I'll have a look for something this weekend and post a link if I find anything interesting.

[smileysnake]

The simple, and perhaps slightly curt, answer to your question is that of course it is a lizard! But this you already knew. The classification of lizard however doesn't necessarily include the presence of legs, as there are numerous legless lizard species around the world. In fact the legless characteristic is really the ONLY thing that snakes and these lizards have in common.

Visually of course a Slow Worm is very snake like, and until you start looking closely many would assume it is a snake. As you rightly say, one difference is the presence of eyelids, but beyond this the skin structure is very different, with many small uniform scales, unlike the large (especially on the underside) and small scales found in snakes. Internally of course the skeletal structure, and the arrangement of the internal organs, easily differenciates the two animal types.

The skeleton of some snakes does indeed retain vestiges of rear legs. In many this is simply a vertabrae in the lower body which could be the remains of a pelvic bone. In others, specifically the larger Boas and Pythons, there is a small pair of claws, or spurs as we call them, either side of the vent (bottom). We often use these as a quick method of determining sex, as the males spurs are larger than the females. The same is found in some turtle species with the front claws.

Of course it is not always so easy to define a species. Recently a new Cobra species was 'discovered'. It was always regarded as a sub-species, but a DNA test showed it to not be biologically related, and so it was reclassified.

[demicav]

Originally Posted by smileysnake

The simple, and perhaps slightly curt, answer to your question is that of course it is a lizard! But this you already knew. The classification of lizard however doesn't necessarily include the presence of legs, as there are numerous legless lizard species around the world. In fact the legless characteristic is really the ONLY thing that snakes and these lizards have in common.

Visually of course a Slow Worm is very snake like, and until you start looking closely many would assume it is a snake. As you rightly say, one difference is the presence of eyelids, but beyond this the skin structure is very different, with many small uniform scales, unlike the large (especially on the underside) and small scales found in snakes. Internally of course the skeletal structure, and the arrangement of the internal organs, easily differenciates the two animal types.

The skeleton of some snakes does indeed retain vestiges of rear legs. In many this is simply a vertabrae in the lower body which could be the remains of a pelvic bone. In others, specifically the larger Boas and Pythons, there is a small pair of claws, or spurs as we call them, either side of the vent (bottom). We often use these as a quick method of determining sex, as the males spurs are larger than the females. The same is found in some turtle species with the front claws.

Of course it is not always so easy to define a species. Recently a new Cobra species was 'discovered'. It was always regarded as a sub-species, but a DNA test showed it to not be biologically related, and so it was reclassified.

Very interesting post Smileysnake. Welcome to WAB.