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Re: Everyone's discussing bird origins...



George Olshevsky wrote:

>Also, I'm pleased to learn from a different post that there is at least one
>living example of a tail-glider.

I think you'd better restrain your enthusiasm on that one, George.  The
feathertail glider (Acrobates pgmaeus) has stiffened hairs on either side of
its tail but these are NOT the primary gliding surface - which is, instead,
a membrane between the front and hind limbs, as on a flying squirrel or a
sugar glider.   According to Strahan, ed., The Mammals of Australia, the
tail assists in steering and braking before landing (as do the tails of many
birds, but that doesn't make them "tail-flyers").  In fact this species has
a relative (the only other member of its family, the feather-tailed possum
Distoechurus pennatus) with the same type of tail but no gliding membrane.
It does not glide, though it presumably evolved from a gliding form.  The
tails of anomalurids (the African "scaly-tailed squirrels) may serve a
similar function - one of them, too, has lost (or never had) the gliding
membrane.
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
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