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Re: Mesozoic mountains & Spinosaur sails with neighboring critters (2 threads)



From: Amtoine Grant <ajgrant@eastlink.ca>
Reply-To: ajgrant@eastlink.ca
To: Subject: Re: Mesozoic mountains?
Date: Thu, 03 Mar 2005 16:39:50 -0400

On Wednesday, March 2, 2005, at 11:41  AM, David Marjanovic wrote:

http://jan.ucc.nau.edu/~rcb7/paleogeographic.html 

Nice link. Looking at the map of the early Cretaceous Earth, it looks
to me like Greenland would be a fantastic place to unearth clues on
spinosaur ancestry and evolution.

Why?

My take on the theory that spinosaurs are derived coelophysids. 

via Dilophosaurus of JP & Bakker fame, yes?

(my apologies for any typoes).

time. If there indeed was a chain of periodic landmasses in the Atlantic Ocean, this affinity with water lends reason to the piscivorous adaptations. It would also explain the recently discussed purpose of the spinosaurs jaws being suited for small(er) prey than more robust-jawed theropods such as allosaurs, megalosaurs & tyrannosaurs. We all [should] know that when animals take up residence on islands, they tend to experience a reduction in body size, so to me this would make perfect sense of the physiology of spinosaurs, except the sail.

maybe the sail was a species-identifier used in courtship, or a Lorenz-like device to keep the hatchlings close by when roaming the open areas away from the nest.


and for those who earlier said that there are no examples of unrelated creatures sharing an enviroment & evolving something like a sail....in modern times, both *Riftia* worms at undersea volcanic vents and at least one type of clam that shares the enviroment down there, both lack internal organs, and both rely on sulfur-processing bacteria inside them.

just a thought.

And no, I haven't taken into account Irritator from South America,

after the Dilophosaurs but before the Baronyx/Spinosaur radiation, a side-branch of the lineage heads "south" into South America?

but then again none of know ALL the answers. Also, if I recall, spinosaurid sizes go from smaller to larger starting in Europe with Baryonx, reaching their peak with Spinosaurus in North Africa. Almost as if the size restraint imposed by island-dwelling was lifted as they moved from my preposed North Atlantic islands to mainland. . . 

interesting idea.

(and even if the Atlantic itself is post-Spinosaur, there are also ecological islands, which might have forced the lineage into smaller sizes).