Yet another transitional fossil found--a snake with legs!

[catsittingstill]

Wow.  Found this via Pharyngula-- (a great site all on its own, by the way, as long as you don't mind atheism).

A fossil of a snake with two hind legs has been found in Lebanon.  One hind leg's bones were visible in the fracture plane of the fossil, the other was buried in the rock that cradled the fossilized bones, and  was imaged with an intense beam of x-rays from the Grenoble (France) synchrotron.

The 85cm-long (33in) creature, known as Eupodophis descouensi, comes from the Late Cretaceous, about 92 million years ago.

(For comparison, amphibians ventured onto land about 360 million years ago, birds showed up about 150 milliion years ago and the non-avian dinosaurs died out 65 million years ago.)

However, according to Wikipedia, snakes with hind limbs are already known from the fossil record.  Plus some existing speciles of snakes, like pythons and boas, have vestigial hind legs called anal spurs that are used in mating. 

The new fossil is still cool, but may be a bigger deal for what it has to tell is about gradual changes in the development of snakes than because it confirms a previously unconfirmed hypothesis.    

For instance modern snakes are practically all thorax (chest)--which is why they have ribs all the way down.  A non-snake spine develops with neck vertebrae, thorax vertebrae, lumbar vertebrae sacral (pelvic) vertebrae and caudal (tail) vertebrae in that order, and their types are controlled by gradients of (probably proteins but I don't know for certain) laid down by Hox genes in a certain order from head to tail before the vertebrae start forming.   Changes in these Hox gene product gradients during embryo formation are reflected by changes in body type--geese have lots more neck vertebrae than we do, and the combination of Hox gene products that tell proto-vertebrae "become neck vertebrae" is more stretched out in the goose embryo.

Well, snakes have become practically all thorax and other vertebra types have been crowded down to a few spots at the ends.  Some modern snakes have some pelvis left--a lot of them don't.  Some modern snakes have anal spurs, but the bones involved don't actually connect to the pelvis bits (if they are even present).  Ancient snake ancestors can presumably help clear up what happened in what order.

So this is very interesting, but not the earth-shaking breakthrough that I thought at first.

Comments

[maiac.livejournal.com]

Before you know it, they'll have found a fossil that looks just like the darwinfish.

[orawnzva.livejournal.com]

You mean like these?

[catsittingstill.livejournal.com]

I think she's holding out for one with DARWIN written on the side :-)

[orawnzva.livejournal.com]

Sarah and I just finished rereading To Say Nothing of the Dog out loud together, and I am thinking of an eccentric professor keeping a prehistoric transitional amphibian as a pet and naming it Darwin.

[catsittingstill.livejournal.com]

:-)

[thatcrazycajun.livejournal.com]

I can't help thinking of the gags the late Johnny Hart used to draw in his "B.C." comic strip: "Snakes got legs!" :-)

[catsittingstill.livejournal.com]

I remember B.C. I think I even remember a snake. I don't remember it having legs, though.

I keep picturing a burrowing snake, with its hind legs scrabbling to brace its body so it can wriggle farther into the soil...

[dan-ad-nauseam.livejournal.com]

I am reminded that Agassiz opposed evolution, arguing that reptiles and birds were a particularly sharply bounded pair of classes. Then the first Archaeopteryx specimen turned up.

[catsittingstill.livejournal.com]

In some ways, every fossil is a transitional fossil--unless it's a member of a species that never produced any daughter species.