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Re: Leaellynasaura, Tails, and Integument

quote from a manuscript of mine:

>>Norell & Makovicky (1999: fig. 21) figure an S-curved,
>>articulated tail of Velociraptor mongoliensis in dorsal view.
>>Tracing the path of the tail axis of the Velociraptor specimen
>>in Rhinoceros 4.0® allows measuring the angle across the
>>first bend as 98° for the first ten caudals, which translates
>>to nearly 10° per intervertebral joint.

That specimen shows extremely elongated zygs. So much for lateral
stiffening...... OK, compared to crocodiles and especially monitors,
this IS limited mobility.

Norell, M.A. & Makovicky, P.J. 1999: Important features of the
dromaeosaurid skeleton II: information from newly collected specimens
of Velociraptor mongoliensis. American Museum Novitates 3282, 1–45.


On Tue, Jul 13, 2010 at 12:29 AM, Dann Pigdon <dannj@alphalink.com.au> wrote:
> On Tue, Jul 13th, 2010 at 4:39 AM, Jocelyn Falconnet <j.falconnet@gmail.com> 
> wrote:
>> "Dorsoventral and cranial expansion of
>> postzygapophyses (up to 44% of vertebral body length) on vertebrae in
>> the terminal half of the tail of L. amicagraphica suggests an
>> alternative to ossified tendons to provide caudal axial rigidity."
>> As far as I understand, the caudal vertebrae of *Leaellynasaura*
>> exhibits several anatomical features seemingly related to the
>> stiffening of the tail, analogous to the adaptations seen in the
>> classical theropod and ornithischian examples. Pretty interesting
>> example of convergent evolution and functional evolution.
> My question is: would such a stiffening system restrict lateral movement of 
> the tail? If the stiffening
> was mainly to hold the tail erect, then perhaps it only had to prevent it 
> from bending in the sagittal
> plane. That might leave enough lateral flexibility to curl the tail about the 
> body - or at least to allow
> the animal to turn around inside a burrow.
> Then again, if the stiffening was mainly present in the terminal half of the 
> tail, might the base of
> the tail be flexible enough for a cute little Leaellynasaura to tuck it's 
> sleepy head and neck under it
> in a suitably adorable fashion?
> --
> _____________________________________________________________
> Dann Pigdon
> Spatial Data Analyst               Australian Dinosaurs
> Melbourne, Australia               http://home.alphalink.com.au/~dannj
> _____________________________________________________________