Science. 1993 Feb 5;259(5096):790-3. doi: 10.1126/science.259.5096.790.
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.
晚侏罗世的始祖鸟被认为是一种适应奔跑的有羽毛的掠食者，它代表了从兽脚亚目恐龙进化而来的真正鸟类的陆地阶段。然而，对爪形结构的研究表明：（i）现代地面和树上栖息的鸟类可以根据爪的弯曲程度来区分，较大的爪弧特征表明树上栖息的鸟类和树干攀爬者，以及（ii）始祖鸟的后足（后脚）和前肢（前脚）的爪子分别表现出适合栖息和树干攀爬鸟类的弯曲程度。在此基础上，始祖鸟似乎是一种栖息鸟类，而不是一种奔跑的掠食者。
