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Re: Mesozoic mountains?



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. I imagine that as the continents spread apart, namely NA & what is now Europe, chains of island would have periodically ascended & descended from the tectonic movements. My support for this comes from the fact that Coelophysids are found in North America[albeit dang-near everywhere], including here in Nova Scotia, the furthest eastward extension of North America. Also, the gracile build, relatively similiar body proportions, and kinked snouts - unless the latter trait evolved again in these theropods, wouldn't be the first 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.
And no, I haven't taken into account Irritator from 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. . .