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RE: Leaellynasaura, Tails, and Integument

  Organ does note however that the tendons have a relationship to motility in 
any fashion, be it where vertebral inflexibility is enforced in the vertebrae 
themselves whether it is dorsoventral or colaterally, or when vertebrae appear 
to be fairly mobile, the lattice structure is either highly reduced and closer 
to the central bodies, or where the neural spines are high and the lattice is 
expanded. That the lattice is practically absent in some groups of 
ornithischians or bird-line saurischians, but present in others, implies not 
only a structural relationship to mobility (even if there was some ability to 
move) but also evolutionary relationship, which is just as prone to stance and 
gait and therefore flexibility.

  The caudal rods in dromaeosaurs are different, however: they are bound into a 
tight cluster several rods deep and several rods wide; while they could 
presumably slide past one another, it seems unlikely such a bundle of bone 
would have permitted too much motion.

  Note that I am not rejecting any motion, but trying to make sure that 
taphonomic process is also being taken into account. At least one dromaeosaur 
tail (GI 100/986) shows a sigmoid aspect in dorsal view; at at least one point 
along the curve, the individual rods are bending away from one another, 
implying a limit to their capability to bend, although permitted more 
posterior/anterior rods to accommodate the curvature of the tail. This at least 
indicates curvature outside of taphonomic distortion; despite this, the 
curvature is weak, and in the Oklahoma *Deinonychus* tails, the rods are often 
splayed out from the curvature of the tail series itself.


Jaime A. Headden
The Bite Stuff (site v2)

"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 

> Date: Tue, 13 Jul 2010 11:44:28 +0200
> Subject: Re: Leaellynasaura, Tails, and Integument
> From: heinrich.mallison@googlemail.com
> To: qi_leong@hotmail.com
> CC: dinosaur@usc.edu
> On Tue, Jul 13, 2010 at 10:57 AM, Jaime Headden  wrote:
>>   curvature appears to be unknown in hadrosauroid tails where a lattive is 
>> present,
> Organ, C.L. 2006: Biomechanics of ossified tendons in ornithopod
> dinosaurs. Paleobiology, 32, 652–665.
> apparently, the lattice pattern does not do too much to block lateral
> motion, IIRC.
> Best
> Heinrich
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