Sunday, September 14, 2008

Hadrosaur 3D chewing computer animation

An article in the latest Palaeontologica Electronica (http://palaeo-electronica.org/2008_2/132/index.html) shows a 3D computer model of an Edmontosaurus skull showing how the skull moves during chewing. One of my labmates, Casey Holiday, is a co-author on this paper. This I find rather interesting, because Casey does not believe what the paper says. The paper does a great job of illustrating how all the synovial joints move during chewing ala the classic pleurokinetic hadrosaur skull. The problem is that in Casey's dissertation, one of the things he showed was that just because one has a synovial joint doesn't mean it moves. Lizards all have wonderfully fragmented skulls with synovial joints all over the place, but are not generally thought to be pleurokinetic, for instance. As Casey demonstrated in his dis, to have a pleurokinetic skull that moves like they show requires a chain of movments that all have to occur. If any one of them are locked into position, the whole thing is stuck, sort of like throwing a wrench into a gear. This happens to be the case with hadrosaurs. What Casey really thinks is going on is that these synovial joints allow the skull to grow quickly, keeping it mobile enough to allow growth, but not so mobile as to move during chewing. Actually, I should say here that this is an overly-simplistic representation of his views and that it is a bit more complex than that, including a certain amount of evolutionary baggage, but you get the point, that being the skulls were actually most likely rather akinetic, i.e. they didn't change their shape every time they bit down on something. So why does his name appear in this paper? He worked out the chewing mechanisms for the group, but the others put together the computer modelling and they went with the classic view rather than what Casey had worked out. My opinion is that Casey is right and will be vindicated later on.

3 comments:

Anonymous said...

Ah....but all the Edmontosaur paper did was retest Pleurokinesis using fancy new methods. One does not have to believe anything if you're just retesting someone else's hypothesis. Maybe they had wiggly skulls, maybe they didn't. The kinesis paper (due out in a week or so) also suggests hadrosaurs must have been doing something funky. we'll write a paper on how to sit on the fence astride major biomechanical hypotheses.

Anonymous said...

and PS, somehow, this post gets 1st dibs on Google search for hadrosaur chewing...whodathunk.

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