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Humps and Sails Re: Hadrosaur necks [was Re: A few species names if you please.]



On Wed, 17 Jan 2001 10:43:23  
 znc14 wrote:
>2) Sailbacks: It was recently suggested that the "sails" of high-spinned
>dinosaurs actually supported buffallo-like humps. Sadly, although a paper
>has been published on the subject, there has never been a formal reply.
>The paper does a good job of showing that tall dorsal spines in dinosaurs
>are morphologically dissimilar from those in "pelycosaurs." However, I am
>personally not satisfied that the paper demonstrated that a "hump" is a
>viable altenative hypothesis. However, rather than dismissing this paper
>offhand, I will await a published rebuttal.

Jack Bowman Bailey's 1997 paper in JVP is, indeed, the only published paper on 
the possibility of "humps" in dinosaurs.  However, a 1990 paper by Charig and 
Milner in _Dinosaur Systematics_ mentions the discovery of an isolated Baryonyx 
neural spine that suggested that Baryonyx had elongated neural spines, which 
may have *possibly* supported a hump.  Later, in Glut's _Dinosaur Dictionary_, 
Glut and William Stout speculated that Ouranosaurus may have had a hump.  

Bailey, in my opinion, succeeded in showing that the neural spines of 
Spinosaurus (and other dinosaurs) differed from those of Edaphosaurus and kin. 
Among other differences, Bailey pointed out that the Spinosaur neural spines 
were massive, broad-beamed, and less "whippy" (tall and narrow) than those of 
Edaphosaurus.  He also compared the spines of Spinosaurus and other dinosaurs 
to those seen in Bison antiquus, which are massive, broad-beamed and do support 
a hump.

Bailey also wrote that these dinosaurs may have possessed humps: Tenontosaurus, 
Montanaceratops, Protoceratops, Acrocanthosaurus, Baryonyx, Becklespinax, 
Dicraeosaurus, Amargasaurus, Hypacrosaurus, Barsbolida, and, of course, 
Spinosaurus and Ouranosaurus.  

Earlier today on the list somebody mentioned, in an unrelated post, that humps 
are utilized by some large animals in order to store food, which can "decrease" 
the metabolic rate and enable the animal to survive for longer periods, and, 
perhaps, to obtain a larger size over time (okay, this is really general and 
simplified, and may not be totally accurate).  If Spinosaurus did possess a 
hump, perhaps this hump may explain why Spinosaurus grew so large.  Jurassic 
Park notwithstanding, Spinosaurus was a large animal, and likely was near the 
upper "limit" for land animals (this nobody knows, but it is an assumption of 
mine).  Perhaps this "hump" (if Spinosaurus did possess one), enabled the 
dinosaur to go for long periods without eating.  In a dinosaur as large as 
Spinosaurus, continuous eating was necessary.  Albeit not as much as in a 
herbivore, this amount of food would have likely been large.  Perhaps a hump 
may have made it easier for Spinosaurus to cope through droughts and !
!
dry periods, and, in an evolutionary sense, enabled this animal to grow to 
large sizes.  

This is just pure speculation, of course, and it is getting late...

Anyway, there was a really good interview with Bailey in the 5th issue of 
Dinosaur World (Summer/Fall 1998).  Three illustrations of hump-backed 
dinosaurs accompany this article, including Ouranosaurus and Spinosaurus.  

Steve

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