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Re: pterosaur femora sprawl
David Peters writes:
Animals generally don't stop locomoting palms down without going through some sort of intervening phase. Apes were suspending themselves from branches before becoming knuckle-walkers, so that's in the same league. Chalicotheres and anteaters, also knuckle walkers, may have just one day decided to "save their nails." I don't know about how they changed patterns. Were some small and arboreal?
Platypus are 'knuckle-walkers', but certainly didn't go through an arboreal
phase. In their case perhaps it's to protect the webbing between the front
toes, or because of the long claws they use to dig burrows.
I suspect knuckle-walking in apes has less to do with climbing, and more to
do with the delicate nature of their sensitive palms and fingers. Dexterous
tool-using hands with sensitive finger tips are at odds with the type of
thick pads required to use the palms to walk on.
It would seem that any quadruped with specialised hands could potentially
become a knuckle-walker, if those adaptations in the hands get in the way of
locomotion on the ground (or vice versa in the case of great apes).
GIS / Archaeologist http://geo_cities.com/dannsdinosaurs
Melbourne, Australia http://heretichides.soffiles.com