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Re: [Re: Origin of feathers]



In a message dated 98-05-04 15:10:29 EDT, archosaur@usa.net writes:

<< How is a stiffened tail helpful in an arboreal lifestyle/ Wouldn't it get
in the way most of the time and wouldn't it make more sense to have a
prehensile or semi-prehensile tail? The more parts of you that are anchored
the less chances that you'll fall right?>>

Yes, a prehensile tail is more helpful than a stiffened tail for some arboreal
lifestyles. The point here is that a stiffened tail is probably more helpful
in stabilizing the glide path or flight path of an animal suited to leaping
than its precursor, which is a flexible tail.
 
<< As for flying, wouldn't a smaller tail be better? It seems that all of the
major flying animals were adopting a trend towards smaller and nonexistent
tails. Dromies and Oviraptors had long tails. So did Herrerasaurs. >>

Evidently you can't jump from a long flexible tail to no tail all at once. The
stiffened tail, presumably because of its utility as a rudder or as a "rear
wing," was a necessary stage in the evolution of flight in pterosaurs and
dino-birds. Once ornithoptering developed, the drag from the tail became
selectively less advantageous than its stabilizing effects. Ornithoptering is
done best with no tail or with a short tail with spreadable feathers, thus the
tail diminished in the more advanced pterosaurs and birds.