Re: Triassic dino tracks in this week's Science

[Dann Pigdon <dannj@alphalink.com.au>]

"Emma C. Rainforth" wrote:
> 
> To reiterate the Olsen et al rebuttal to Thulborn: these prints DO
> NOT resemble Eubrontes. Period. What we see, from the ONLY EXTANT
> specimen - a plaster cast - looks like a poorly preserved
> "crurotarsan"  (i.e. sinmilar to Parachiroterium, or some of
> Ellenberger's taxa from the Upper Triassic of Lesotho). 

The image available of the plaster cast isn't all that clear. Did Olsen
et al look at it personally, or the prints themselves for that matter?
There has been many a thread on the DML regarding the dangers of making
interpretations based on illustrations or photos alone.

> Incidentally
> Ellenberger's - some of which are nicely preserved and happen to have
> only 4 pads on digit IV, thuis TOTALLY PRECLUDING a dinosaur origin -
> are found in association with Grallator.

Okay, so association isn't strong evidence.

> >I don't know anything about pseudosuchians, but would any of them have a
> >pes stride length of 2m?
> 
> uh, so, um, what Eubrontes (sensu stricto) for that matter has a
> stride length of 2m????

The real question is whether these Aussie prints are theropod or not. A
stride length of 2m suggests a long-legged beast made them. Again, I
know nothing about pseudosuchian anatomy, but would it have been
physically possible for one to have made pes prints 2m apart? 

A quick google image search of 'pseudosuchian' gave me only two images.
One was of a quadruped (the 3m long *Shansisuchus shansisuchus*), the
other of a semi-quadruped in a fast bipedal run. Could a pseudosuchian
large enough to make 43cm prints have been capable of walking (since
these appear to be walking, not running, traces) bipedally and have a
stride length of 2m? Even if manus prints have not been preserved, would
the pes prints have ended up 2m apart even in a quadrupedal 'trot'?

If the tracks don't fit, you must acquit.

-- 
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Dann Pigdon                   Australian Dinosaurs:
GIS / Archaeologist         http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://www.alphalink.com.au/~dannj/
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