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Re: climbing dromaeosaurs and friends



In a message dated 12/7/00 9:26:24 PM EST, scott_hartman@hotmail.com writes:

<< As I mentioned (briefly) in my talk at SVP, the parasagital limbs of 
theropods 
 put their center of mass too far away from the substrate (branches) to have 
 been succesful scannsors.  If they had tried to jump from branch to branch, 
 they would have fallen on the very first try.  This appears to have been 
 true even of Archaeopteryx, and it is unlikely that early birds were 
 arboreal themselves until they evolved a degree of control that allowed for 
 low speed landings. >>

You have to think in terms of theropods that had large/long forelimbs--about 
the same length as the hind limbs--not the shortened forelimbs that occur in 
the more derived terrestrial, cursorial members of of the order. Rather like 
theropod squirrels or monkeys. The earliest archosaurs were rather small, 
quadrupedal animals in which the fore and hind limbs were of approximately 
the same length, and the earliest tree-climbing dinosaurs would have been 
quite similar to these. Likewise, the least derived dinosaurs (sauropods and 
prosauropods) were also quadrupedal with relatively long forelimbs. It is far 
more likely that wings evolved in plesiomorphic, small, long-forelimbed 
archosaurs than in derived, large, short-forelimbed, cursorial bipedal 
theropods.