Evidence from claw geometry indicating arboreal habits of archaeopteryx.

The Late Jurassic Archaeopteryx has been thought to have been a feathered predator adapted to running that represented a terrestrial stage in the evolution of true birds from coelurosaurian dinosaurs. Examination of claw geometry, however, shows that (i) modern ground- and tree-dwelling birds can be distinguished on the basis of claw curvature, in that greater claw arcs characterize tree-dwellers and trunk-climbers, and (ii) the claws of the pes (hind foot) and manus (front hand) of Archaeopteryx exhibit degrees of curvature typical of perching and trunk-climbing birds, respectively. On this basis, Archaeopteryx appears to have been a perching bird, not a cursorial predator.