Field of Science

New Triassic Critter Reconstruction II

Here is another new Late Triassic critter reconstraction from the Chinle/Dockum courtesy of Jeff Martz. As with the last one I'll leave the ID up to you with discussion to follow.


13 comments:

  1. Amateur guess: This pic looks similar to some google image search results for "Postosuchus", although there seems to be some disagreement about the size and shape of the forelimbs. Anyway, I just wanted to check in and let you know that I've enjoyed reading your blog, Bill, and am very impressed with your diligence in posting. Now I'll step aside and wait for the expert guesses to roll in.

    - Steve Clarke

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  2. If you want to keep it a secret, you should probably obscure the filename next time....

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  3. Hey, I swear I didn't look at the file name.

    - sc

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  4. Well...Nice Christmas Present...
    Is it Postosuchus kirkpatricki or P. alisonae?
    Hmmmm....

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  5. Pretty cool, makes me wish I had an extra wide monitor to use it for wallpaper. :-)

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  6. I would also love a wallpaper! I was going to say Postosuchus, too. Wonderful reconstruction.

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  7. Any rationale for the bipedal vs. quadrupedal reconstruction?

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  8. Steve,

    Thanks, glad you enjoy it.

    Mike,

    I knew the file name would get me but I was literally posting on my was out the door for two days with family (trying to keep up with my diligent posting). Maybe next time I'll fake the file name.

    Georgios,

    If you look very closely at the manus you will see that there is no surface evidence for a groove in metacarpal 1 for contact with metacarpal two, therefore it is clearly P. kirkpatricki. ;)

    Randy,

    Obviously Jeff has reconstructed the animal as bipedal following Jonathan Weinbaum's (Jeff's bestest buddy)interpretation. Jeff and I have gone round and round on this as I feel that Postosuchus was quadrupedal. Why? Because it looks cooler as a quadruped and dorky as a biped (Don't you wish all science was that simple?) More on this in a bit.

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  9. A few comments: Both the holotype and paratype of Postosuchus kirkpatricki in the TTUP collections have excellent forelimb (and hindlimb) material, and the North Carolina specimen has ARTICULATED hands and feet, so there is little or no question about how to reconstruct either, or the rest of the skeleton for that matter; the TTUP material covers nearly the entire skull and skeleton, and Jonathan Weinbaum's skeletal reconstruction (which I used) is probably pretty reliable. Contra Peyer et al, I agree with Jonathan that there is really no doubt that the holotype and paratype represent two individuals; the morphology on individual elements is identical, the size differences of these elements between the larger holotype and smaller paratype are consistent, and there is no part duplication. Chatterjee's field notes (which I have probably spent more time poring over than anyone), confirm that the specimens were found in two concentrations separated by several meters (the quarry map in his 1985 paper probably shows them too close together). The only question is whether Postosuchus was bipedal or quadrupedal or not. I am coming around to Jonathan's view that Postosuchus may have been an obligate biped, or close to it, simply because the forelimbs are so short compared to the hindlimbs, not to mention the stupid little thalidomide baby hands. I have toyed a little with a quadrupedal reconstruction, but have had a hard time making it work, especially in getting the forelimb stride length to match the hind limbs without forcing the latter to take little baby steps.

    LNJ

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  10. Oh my.

    Holy Parallel Evolution, Batman!

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  11. I have to side with Bill on this one - I think it was probably quadrupedal. I'm not so sure the forelimbs are as short as they seem. I'm willing to bet that the forelimb/hindlimb ratio isn't much different than other suchian archosaurs. That said, I'm talking out of my arse, because I haven't actually done the measurements or calculated the ratios.

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  12. Weinbaum (2008) gives the front/hindlimb ratio as 59, which really is not that much of a difference. Tyrannosaurs are in the 80s and Allosaurus and Coelophysis are in the 70s. Some more on this soon.

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  13. I remember when Sankar Chatterjee first talked about Postosuchus and that it was a bipedal 'thecodont'. Just about everyone laughed or dismissed it. Glad to see he was right.
    Tracy Ford

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