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Re: origin of bats
With regard to non-volant locomotory abilities: Onychonycteris
hyper-folds its hands at the wrist/metacarpal joints, like all bats
do. Evidently it was not using its hands like most quadrupedal
tetrapods do. And the bipedal hypothesis still stands. Claws and all.
Keep in mind that the distal wing could be functional in some climbing
maneuvers, but still be folded away in typical bat style during rest.
The lingering of the claws suggests that they might have been important
very close to the origin of flight (or simultaneous with it); that's
the point being made, anyway.
Body parts don't disappear immediately after cessation of use. But
they do disappear eventually. Case in point: Fruit bat (flying fox)
manual digit II ungual. Analogy: hind limbs on primitive whales.
The digit II claw in flying foxes is not entirely non-functional. They
are also quadrupedal suspensory climbers, mostly via digit I of course,
so we might suppose that the loss of the other claws and the evolution
of extreme folding in the wing simply moved the quad climbing loads to
the first digit. Doesn't seem to speak to bipedalism specifically.
Michael Habib, M.S.
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205
(443) 280 0181