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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 <DragonsClaw@gmx.net>:
> "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