Primitive snakes

[JimmyDavid]

Primitive is relative to ancient.
I guess everybody agrees that evolution takes a lot of time. Therefore, an ancient species has had more oportunity to perform changes than a modern species.
I don't understand why scientists say that Boas & Pythons are the most primitives snakes because (get this).....they still show remains of lizard bones from where they evolved!!!!!!!?????

That's exactly PAINT-FRESH evolution, it proves that they haven't been around long enough to get rid of those traces.

Anyone else starting to see it my way?

[Katt]

Boids are more primitive than colubrids, relatively speaking b/c colubrids have evolved enough to lose these bone remnants.

[CamHanna]

an ancient species has had more oportunity to perform changes than a modern species.

When an ancient species performs these changes does it not become a modern species?

I don't understand why scientists say that Boas & Pythons are the most primitives snakes because (get this).....they still show remains of lizard bones from where they evolved

That's exactly PAINT-FRESH evolution, it proves that they haven't been around long enough to get rid of those traces.

Boids also lack the venoms of advanced snakes (vipers, colubrids, elapids).

It takes a lot of time and the proper circumstances to become a snake. The current theory is that when varanid-like-lizards became more fossorial they lost a lung, their eyelids and their eyes. The eyes reformed after these "pre-ophidian squamates" emerged from their burrows. This explains why snakes have a similar eye structure to one another and why this eye is different than that of other animals. Boids have the 'snake-eye', and not a left lung or eyelids. From these point it is evident that boids evolved from the same squamates as other snakes did, however they evolved less, so they are more primitive. I suppose that the 'advanced snake line' could possibly have existed before the 'boid line'. If I had the initiative I'd dig around the Internet for fossil records to provide dates; but I don't.

Cam

Edit: The definition of primitive:

From http://dictionary.reference.com/search?r=2&q=primitive
Biology. Occurring in or characteristic of an early stage of development or evolution.

That's a boa my friend.

[Double J]

It is doubtful that there was a seperate "advanced snake line" that evolved convergently and seperately from the more primitive snakes. There are far too many derived traits that it would be unlikely that a seperate evolutionary line from the original snakes would have yielded them.

Primitive..... this is often a loaded term..... it works well for things on a biological basis... but runs into trouble when used on a cultural level. That said... primitive seems to have a stigma attached to it. Why is primitive undesirable when referred to on a biological level? These "primitive" animals have had to change "relatively" little over the course of millions of years.... I consider this to be rather successful. In terms of evolution, if there is little pressure to change, little change will occur other than for reasons of genetic drift and genetic isolation. What makes colubrids, elapids, and vipers so different from boids and pythons is that the evolutionary split occurred so long ago.... 50+ million years of divergent evolution will yield a lot of things, and that is why we have such a wonderful amount of diversity with respect to snakes.

Now for Jimmy..... boas and pythons aren' exactly "paint fresh" Instead, they bear much resemblance to the earliest snakes.... the fossil record shows it... and I beleive fossils show that the first snakes came about in the neighborhood of 55-70 million years ago... though I cannot remember the number exactly. Let's not forget, these earliest forms are responsible for everything today. Snakes simply diverged very early on as there seems to have been a number of niches to fill in after the extinction of the dinosaurs, not to mention whatever else went with them. This is why we have such a rich diversity today. So, you could say that snakes came about in the right place at the right time geologically speaking.... exploited whatever niches were available (there seems to have been a lot of them), and time and evolution did the rest to give us the current level of diversity. Though of course, this is simplified.
I am at the Porter U of W library as I am typing this... perhaps I will dig up a paper on the subject.

Double J

[CamHanna]

It is doubtful that there was a seperate "advanced snake line" that evolved convergently from the more primitive snakes. There are far too many derived traits that it would be unlikely that a seperate evolutionary line from the original snakes would have yielded them.

Somewhere in ophidian evolution boids and advanced snakes diverged. By "advanced snake line" I meant the snakes that eventially, after this divergence, became colubrids, vipers, elapids and so on. I did not mean to imply that Henophids and Xenophids evolved entirely seperatly.

Cam

[Double J]

Ok.. thanks Cam.. I have re-read what you have originally posted, and realized I misread it originally

Sorry about the confusion.

Double J

[JimmyDavid]

[QUOTE]
[B]When an ancient species performs these changes does it not become a modern species?

Quite right, and that's my point.
Notice that a useless trait goes away much faster than a usefull one. What good
does it do having remains of leg bones in a snakes body? If boids are so old, they would have had more than enough time to get rid of those, wich proves that they could have "parted" from lizards not that long ago.
A very usefull trait like having venom, could be gainned much faster since it's directly connected to survival.

[Removed_2815]

Originally posted by JimmyDavid
What good does it do having remains of leg bones in a snakes body?

Vestigial spurs are used during courtship; they are still important anatomical features that have not been lost during evolution.
If females are more receptive to males who actively use their vestigial spurs to initiate copulation, then males who do this will be better able to pass on their genes. The offspring will be that much more likely to also have these vestigial spurs and utilise them during courtship. Thus, this anatomical feature should be retained indefinitely.
Cheers,
Ryan

[Removed_2815]

double post

[Double J]

Originally posted by JimmyDavid
Notice that a useless trait goes away much faster than a usefull one. What good
does it do having remains of leg bones in a snakes body? If boids are so old, they would have had more than enough time to get rid of those, wich proves that they could have "parted" from lizards not that long ago.
A very usefull trait like having venom, could be gainned much faster since it's directly connected to survival.

The thing here is.. that if there is no *selective pressure* to losing a body part, there is no immediate necessity to get rid of it. If a vestigial or useless trait has no affect on fitness, then there is no pressure to lose it, and therefore animals that have it are able to reproduce and pass on the genetic material that expresses this useless trait or vestigial body part. Simply because a body part is useless does not always mean that animals with it will be selected out if it has no immediate disadvantage. Thus, since a vestigial body part may not "do any good"... if it does no harm, there is no pressure to select it out.

As Ryan pointed out, there has actually been a selective pressure *to keep* an otherwise vestigial body part in the case of pythons, as females are generally more receptive to makes using their vestigial spurs. Though this trait is not "directly related to survival," it has proven to be important for breeding nonethless.

Evolution is a beautiful thing.

[JimmyDavid]

Double j, i'll have to disagree there. The first rule of evolution is: USE IT OR LOSE IT.
Anyway, why is it that colubrids have no spurs? Wouldn't came IN HANDY as well for courtship?

Katt, i want you to read your own post v-e-r-y s-l-o-w-ly to yourself. Can you see the logic flaw there, yet? Shouldn't it be the other way around?

[Removed_2815]

Originally posted by JimmyDavid
Double j, i'll have to disagree there. The first rule of evolution is: USE IT OR LOSE IT.

But primitive snakes do use their vestigial spurs, and it would appear that there is a selective pressure favouring the spurs (if females are, in fact, more receptive to mates that use them to initiate copulation). They "use it"; hence they will not "lose it" until such an appendage no longer confers a selective advantage upon the user.
Cheers,
Ryan

[Removed_2815]

Originally posted by JimmyDavid
Anyway, why is it that colubrids have no spurs? Wouldn't came IN HANDY as well for courtship?

This is the point of your original post, isn't it? Colubrids are more "advanced," they have evolved different characteristics that set them apart from their primitive counterparts. Not all characteristics are universal across a taxon; colubrids may be the result of when such an appendage no longer conferred a selective advantage upon the user. Hence, they did not "use it" so they were destined to "lose it."
Cheers,
Ryan

[Double J]

Originally posted by JimmyDavid
Double j, i'll have to disagree there. The first rule of evolution is: USE IT OR LOSE IT.

Sorry, you are wrong here.

This is a common misconception that is not entirely true. Evolution is all about selective pressures. Adaptation then is a change in structure or behaviour, based on genetics to respond to an environmental pressure or stressor.

If there is no pressure to have or get rid of something, then there will be no sexual or environmental selection of individuals in that direction. Often traits that are neither advantageous nor detrimental are lost due to genetic drift, or that there is no pressure to keep that trait, so it slowly wanes out.

Still, I can name off a laundry list of unnecessary features of any number of animals, but they still have them because it is NOT ADVANTAGEOUS to get rid of them even though it is not advatageous to keep them either. If a trait does not result in death before reproduction, or prevent reproduction due to undesirability to mates, the genetic material that expresses that trait will be passed on and will likely expressed in the offspring in many cases.

Double J

[spidergecko]

Originally posted by JimmyDavid
Double j, i'll have to disagree there. The first rule of evolution is: USE IT OR LOSE IT.

That is most definitely not true. Species can carry vestigal and useless pieces for their entire existence. The first rule of evolution is: IF IT KILLS YOU BEFORE YOU CAN REPRODUCE, YOU LOSE IT.