Shubin et al. (2004) have found an interesting new fragmentary fossil of a late Devonian tetrapod, one that they suggest represents a new transitional form between the distinctly fishy Panderichthys and the significantly more amphibian-like Acanthostega.
It is 'only' the humerus, or upper arm bone, but this is a significant part of the animal, since it is these limbs that were undergoing a transformation as the lineage evolved away from the water and towards a more terrestrial lifestyle. The experts suggest that the structure of this particular limb was not appropriate for crawling on land, but was a step away from the paddles of a fish and was part of a stout limb that could have propped up the heavy, bony head of this predator as it lurked on the bottom.
Continue reading "Uh-oh. Evolutionists discover two new gaps in the fossil record!" (on Pharyngula).
3 Comments
Chris Thompson · 1 April 2004
Some things bear thinking about when you read something like "paleontologists have found a femur and reconstructed a skeleton". First, consider human skeletons. We have 206 bones. Some of these are unique: the bones of the spine, the sternum, and some of the skull.
But, if you find one femur, you know what the other one looked like. That goes for most of the bones of the "appendicular skeleton"- the skeleton other than the skull, spine, etc. And if you know the size and shape of the femur, you have a very good idea of what the tibia and fibula looked like. You also know a lot about the size and shape of the hip bone, and once you know those, you can make educated guesses about the size and shape of the bones of the upper body, too.
How?
Well, despite what antievolutionists would have you believe, the skeletons of terrestrial, quadrapedal (and bipedal) vertebrates bear amazing similarities to one another. So, based on what we see in other, better-known organisms, we make sound estimates of what we would find in newly discovered fossils. Don't let anyone fool you into thinking this is anything new: one of the greatest catastrophists of science, Georges Dagobert, Baron Cuvier, also considered to be one of the greatest thinkers of all time, based his work on the "correlation of parts". And much of his work- minus the repeated catastrophes he had to postulate in order to account for speciation- has held up since 1800.
Ta,
Chris
Nick · 1 April 2004
I guffawed at that excellent headline, PZ! Brilliant!
The discovery of the two new gaps is also reported on by Scientific American,here .
Savagemutt · 2 April 2004
As a layman, I think Chris' comment was a nice follow-up to the article. Has a FAQ about how paleontologists "reconstruct" bodies from limited fossil evidence ever been posted on the Talk.Origins Archive? I don't recall ever seeing one and I think it would certainly make a nice addition.