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RE: Leaellynasaura, Tails, and Integument



  The asymmetrical haemal arches (as in other ornithischians) refers to the 
"flag-shaped" form seen in *Gasparinisaura cincosaltensis,* if what I remember 
of seeing a photo of the specimen is accurate. I'm not sure this would have a 
stiffening effect on the tail at all, however. What does appear to have a 
stiffening effect would be processes that extend and overlap over the 
preceeding (or succeeding) vertebrae from the zygapophyses and/or the haemal 
arches. What I get from the abstract, which I wasn't present to watch and 
cannot now recall the photo I saw, is that the postzygapophyses bear an 
elongated cranial process, the same orientation of different origin as in, say, 
tetanuran prezygapophyses, and about as elongated. One should expect 
limitations of movement, but not excessively so.

Cheers,

Jaime A. Headden
The Bite Stuff (site v2)
http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)





----------------------------------------
> Date: Mon, 12 Jul 2010 20:39:11 +0200
> From: j.falconnet@gmail.com
> To: DragonsClaw@gmx.net
> CC: dinosaur@usc.edu
> Subject: Re: Leaellynasaura, Tails, and Integument
>
> Well, I'm just quoting Matthew Herne (2009). He also mentioned the
> presence of asymetrically expanded haemal arches, shared with other
> ornithischians. As I am not quite familiar with those animals, I can't
> tell you more. If some kind ornithischiophile DMLer could help us
> regarding this matter... please enlighten us ! :-)
>
> Let's see what Matthew Herne said regarding this issue.
> Here is the abstract published in the SVP Meeting issue (in extenso):
>
> POSTCRANIAL OSTEOLOGY OF *LEAELLYNASAURA AMICAGRAPHICA* (DINOSAURIA;
> ORNITHISCHIA) FROM THE EARLY CRETACEOUS OF SOUTHEASTERN AUSTRALIA
> HERNE, Matthew, The University of Queensland, Brisabne, Australia
> *Leaellynasaura amicagraphica*, a small bipedal ornithischian dinosaur
> from the Early Cretaceous (late Aptian-early Albian) of Victoria,
> Australia, is based on an articulated partial upper jaw and
> infratemporal region (the holotype). A skull roof (including a partial
> cranial endocast) and a partial, articulated postcranium have also
> been referred to this taxon, and have been regarded as belonging to
> holotype individual. Another partial postcranium, NMV P186047, is also
> considered to be referrable to *L. amigraphica*. The taxon was
> originally assigned to ‘Hypsilophodontidae’, but more recently has
> been considered a nondryomorphan iguanodontian. Of the postcranium,
> only isolated referred femora and a tibial pathology have been
> described. In this work I describe the osteology of two articulated
> postcrania referred to *L. amicagraphica*. Autapomorphies in the
> haemal arches unite individuals. A caudoventrally expanded postpubic
> process is shared with *Macrogryphosaurus* and *Camptosaurus*, and
> asymmetrically expanded terminal haemal arches with
> *Macrogryphosaurus*, *Gasparinisaura* and *Parksosaurus*.
> Iguanodontian affinities are further supported by the caudoventral
> expansion of the ischium and femoral morphology. Pes morphology and
> the lack of ossified caudal tendons in *L. amicagraphica* is
> plesiomorphic at the level of Ornithischia. The lack of a tab-shaped
> obturator process, extended ischial shaft symphysis and high caudal
> vertebrae number with protracted vertebral body elongation are shared
> with basal thyreophorans; thus, past referral of *L. amicagraphica*
> postcrania to Ornithopoda may be problematic, and the postcranial
> material is at best referrable to Genasauria. Caudal vertebral count
> in *L. amicagraphica* (>70) is the highest recorded for a
> non-hadrosaurid ornithischian. 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 ossifi ed tendons to provide caudal axial rigidity.
> Caudal vertebral morphology suggests a hyper-extended tail of
> approximately three times estimated pre-caudal body length.
>
> 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.
>
> Cheers,
> Jocelyn
>
> 2010/7/12 TooTs :
>> "anterior and dorsoventral elongation of
>>>
>>> postzygapophyses"
>>
>> Just to be sure: is that supposed to mean "elongated pre-, post-
>> zygapophyses, and chevrons". Similar to the condition observable in
>> Dromaeosauridae and Microraptoria?
>>
>> Greets!
>> Torsten
>>
> --
> Jocelyn Falconnet
                                          
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