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Re: Rhamphorhynchus wrist articulation



Quoting "James R. Cunningham" <jrccea@bellsouth.net>:

When perching (assuming Rhamphorhynchus did) would digits I-III foace fore
or aft?

They are unlikely to have been able to perch, but if they did -- digit I would
be directed outboard. Digit II would be directed outboard and aft a bit.
Digit III would be directed aft and outboard. The reason being that
attachments to Digit IV will hyperextend them outward and aft as Digit IV
itself hyperextends into the folded position. The wingfinger is fully flexed
when in soaring flight position and fully extended when folded in the
terrestrial position. The elbow will also be directed fairly far outboard and
somewhat aft.


In other words, could pterosaurs rotate their wrists or were they
fairly fixed in position.

As the elbow is extended, the entire wrist swings aft and down relative to the
r/u. As the wrist itself is flexed, it swings forward and down (sort of like a
cocked-pin joint). The wrist itself does not rotate about the long axis of the
r/u. However, metacarpal IV can rotate about 20 degrees about its long axis,
on a mortise and tenon articulation between it and the distal carpal.

Just out of curiosity, is this all specific to *Rhamphorhynchus*, or does it apply to pterosaurs generally, based on, say *Quetzalcoatlus*?


--
Nick Pharris
Department of Linguistics
University of Michigan

"Creativity is the sudden cessation of stupidity."
    --Edwin H. Land