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RE: Concavenator has two humps



  My assumption -- and this is a big one -- is that the authors imply the 
sacral region between the high, rounded ends of the anterior caudal spines and 
the high, rounded ends of the posterior dorsal spines would have been 
continuous across the intervening sacrals. As the prese4rved slabs doesn't seem 
to show ANY sacral spines, I am guessing (again, BIG assumption here) that they 
are _imperfectly_ preserved, and making any arguments on what shape the hump 
had based on the absence of data (no sacral spines preserved) is premature at 
the LEAST. Occam's Razor implies drawing a straight line or at worst a slightly 
rounded profile from the dorsals to the caudals, and suggests that the sacrals 
were at least as high as the caudals and dorsals preserved to either side.

  On the issue of "hump" versus "sail," I am fairly certain that _mammalian_ 
"humps," mostly bone-supported, muscular contrivances, have little if any 
relationship to the thin, often conjoined relationship of the spines of some 
theropods and some ornithischians with "sails," such as the aforementioned 
*Ouranosaurus nigeriensis*. Expansion of the distal end to support large 
tendons (again, as in _mammals_) is a "hump" devised almost singularly to 
support the nuchal ligaments and thus the head; not muscular humps, as in 
camels, have no neural spine elongation to correlate with, and may be 
indistinguishable at the osteological level with non-humped camels. (More 
assumptions!!)  

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: Wed, 8 Sep 2010 23:32:33 -0400
> From: GSP1954@aol.com
> To: dinosaur@usc.edu; vrtpaleo@usc.edu
> Subject: Re: Concavenator has two humps
>
>
> In a message dated 9/8/10 8:01:04 PM, heinrich.mallison@googlemail.com
> writes:
>
> << I'd be very careful about jumping to conclusion about a "sail". >>
>
> Heinrich should be very careful about actually reading what a message says,
> I never actually said that this specific theropod's tail had a sail in my
> previous message, I merely noted that the thesis that sails in general
> carried fat deposits is questionable. In any case the Concavenator tail base
> neural spines are much taller than normal in theropods so a muscle function is
> dubious.
>
> GSPaul
>
>