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Re: Dinosaurs Breathed Like Birds



> Date: Sat, 16 Jul 2005 04:59:16 +0000
> From: Michael Mortimer <mickey_mortimer111@msn.com>
> 
>> Sauropods (and other sauropodomorphs) have pneumaticized bones--it
>> is a saurischian or eusaurischian trait.
> 
> Er... I'm unaware of any sauropodomorphs more basal than eusauropods
> having pneumatized bones.  Some basal forms have hollow bones, but
> these have no connection to air sacs.

Matt Wedel briefly discusses pneumatic structures in the cervicals of
_Thecodontosaurus caducus_ in:

        Wedel, Mathew J.  2004.  The origin of postcranial skeletal
        pneumaticity in dinosaurs; pp. 443-445 in J. Buckeridge and
        Y. Chen (eds.), Proceedings of the 19th International Congress
        of Zoology.  China Zoological Society, Beijing.

Not the easiest publication to get hold of, perhaps, but I'm sure he'd
be happy to send you a reprint.  The relevant section is as follows
(from a pre-publication ms., so the final version may differ a
little):

        The Late Triassic (Norian) forms _Thecodontosaurus
        caducus_ and _Coelophysis bauri_ are the
        earliest-diverging sauropodomorph and theropod,
        respectively, with unequivocal evidence of PSP [=
        Postcranial Skeletal Pneumaticity].  _T. caducus_ and
        _C. bauri_ may have inherited systems of pneumatic
        diverticula from a common ancestor, but they are the
        first representatives of their separate lineages in
        which the diverticula invaded the postcranial
        skeleton.  _T. caducus_ differs from other species of
        _Thecodontosaurus_, and from all other prosauropods,
        in having sharp-lipped cavities on the lateral sides
        of cervical vertebrae six through eight (Yates, 2003).
        The placement of these cavities on the vertebrae,
        their invasive nature, and the presence of a sharp lip
        of bone bounding each cavity, all argue for the
        interpretation of these cavities as pneumatic in
        origin.  Pneumatic cavities of this sort do not
        reappear in sauropodomorphs until the advent of basal
        sauropods, such as Shunosaurus, which have pneumatic
        cervical vertebrae.

Hope this helps.

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