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China’s Feathered Dinosaurs
Detail of Protarchaeopteryx left hand,
showing close-up of the thumb bone
that in life supported a hooked claw
CLOSE WINDOW
special modifications for grasping one would expect to find in arboreal creatures. For example, the
first toe does not oppose the others and the toe bones shorten toward the claw, rather than lengthen
as they do in birds with grasping feet.
Of course, just because specialized structures often perform specialized functions does not mean those
functions cannot also be performed with less specialized structures. Thus the absence of grasping
characteristics in Caudipteryx and Protarchaeopteryx does not mean that these small theropods could
not climb trees—or at least scamper up through low brush. But to be unable to exclude the possibility
of an arboreal stage in the evolution of flight is not the same as having positive evidence for it. So far
as is known, the anatomy of basal maniraptors is consistent with that of ground-dwelling runners, not
tree-dwelling climbers.