"What about penguins?" I was my immediate thought, "when they move across
ice on their bellies?" But I believe that they too only push themselves
forward with their hindlimbs, yes?
On May 21, 2006, at 2:27 PM, Tim Williams wrote:
Graydon wrote:
Birds did eventually find a way to get the forelimb involved in
locomotion again, but no quadrupedal stance.
One minor point, which doesn't really detract from your statement, which
is essentially correct given that no modern bird uses quadrupedal
locomotion when on land. But the first birds (like _Archaeopteryx_,
confuciusornithids, and so forth) probably used all four limbs when
climbing trees. Thus, they were arboreal quadrupeds and terrestrial
bipeds. The same is probably true for microptorans and
_Epidendrosaurus_.
Among modern birds, juvenile hoatzins are arboreal quadrupeds. Certain
shearwater species have observed using their wings when climbing up tree
trunks.
Cheers
Tim