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Re: Fingers crossed



In a message dated 8/12/98 3:38:45 PM Eastern Daylight Time, TomHopp@aol.com
writes:

<< I'd like to propose feathers. >>

Me too, but for different reasons.  It seems possible to me that the thumb
(digit I) was being pulled away from digits II and III after death by
shrinking of something akin to the Patagialis longus tendon of modern birds.
The Patagialis longus muscle in modern birds connects the shoulder area of the
wing to the carpometacarpus via a connection to digit I and forms the leading
edge of the wing.  Accessory Patagialis muscles also allow fine motor control
of digit I--to which is attached the three small flight feathers of the alula.
Digits II and III are controlled by a separate battery of muscles--among them
the extensor carpi and flexor carpi ulnaris muscles which control the outer
areas of the wing.

If my reading of these muscle attachments is correct (and I am no pro at this)
and if this is similar to the ancestral condition, then the fossils with the
crossed fingers may be showing us that a patagium was present in these animals
and that digit I was functionally separate from digits II and III.  One
explanation for this functional separation may have been the control of
secondary and/or primary remiges on the wing by digits II and III.

For what it's worth.