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Re: giant birds
>>I agree with that George's hypothesis requires a good deal more
transformations (and not to mention missing fossils) than the ground-up
hypothesis, but I disagree that the ground-up hypothesis is simplier than
the trees-down hypothesis. For some reason, everybody follows Ostrom's
(1974, 1979) interpretations of certain features shared by theropods and
birds as being primarily predatory adaptations. An equally good, if not
better, case can be made for tree-climbing adaptation. If anyone denies the
similarity of the maniraptoran forelimb compared to the _Cynocephalus_ (an
obvious climber and glider) forelimb and argues for a closer similarity to
the forelimb of a wolverine (a predator that actively uses its forelimbs)
I'll seriously wonder about somebody's mental health. Think about it: long,
strong forelimbs, flexible wrist, long fingers and strongly recurved claws.
Maniraptorans sound like at least potential climbers.
Actually (this is kind of funny) wolverines share all of those features (except
for the long arms) and _do_ climb trees habitaualy. In fact, all of the extant
predators that I can think of that bring their arms into play (i.e. weasles and
cats) are also fairly good tree climbers. It seems that all those climbing
adaptations are serendipitously good as grabbling adaptations, or is it the
other way around? Hmmm.