Archaeopteryx weak flight abilities. "Archaeopteryx" continues to play an important part in scientific debates about the origin and evolution of birds. Some scientists see it as a semi-arboreal climbing animal, following the idea that birds evolved from tree-dwelling gliders (the "trees down" hypothesis for the evolution of flight proposed by O. C. Marsh). Other scientists see "Archaeopteryx" as running quickly along the ground, supporting the idea that birds evolved flight by running (the "ground up" hypothesis proposed by Samuel Wendell Williston). Still others suggest that "Archaeopteryx" might have been at home both in the trees and on the ground, like modern
Archaeopteryx are limited to a sort of "proto-down" not dissimilar to that found in the dinosaur "Sinosauropteryx": decomposed and fluffy, and possibly even appearing more like fur than feathers in life (although not in their microscopic structure). These occur on the remainder of the body—although some feathers did not fossilize and others were obliterated during preparation, leaving bare patches on specimens—and the lower neck. There is no indication of feathering on the upper neck and head. While these conceivably may have been nude, this may still be an artefact of preservation. It appears that most "Archaeopteryx" specimens became embedded in anoxic