The archaeopteryx is a rather unassuming creature prevalent during the upper Jurassic, known from a mere handful of fossil skeletons preserved in museums. Though the humble animal was only about the size of a crow, its importance in the field of paleontology is immense, as it provides compelling evidence that modern birds are the direct descendents of a particular type of dinosaurs, the raptors. Archaeopteryx had wings, feathers, and a beak, but it also possessed the tail, teeth, and skeletal structure of a reptile. Its status as a transitional creature has sparked much debate over whether it was capable of powered flight, could only glide, or was perhaps limited to the ground.
A Terrestrial Bird?
A small number of scientists, including John H. Ostrom in a 1979 paper (Ostrom.1979. Bird flight: how did it begin? American Scientist 67:46-56), contend that Archaeopteryx was not capable of flight at all, and that it possibly used its feathered wings to trap insects. It has been largely established that feathers evolved before flight; feathers are actually modified reptilian scales that might have provided effective thermoregulation in flightless creatures that possessed them. However, despite the lack of powerful flight muscles in Archaeopteryx, most scientists agree that the evidence points toward at least some flying ability.
Running Start
A 1999 paper by Burgers and Chiappe (Phillip Burgers & Luis M. Chiappe. 1999. The wing of Archaeopteryx as a primary thrust generator. Nature 399, pp. 60-62) proposed a scenario whereby Archaeopteryx could take off from the ground, as modern birds do, but only from a long running start. They felt that the creature would be able to generate enough thrust with its wings in this manner to overcome its various limitations. This point of view has some tenuous support, but the vast majority of those in the field have focused on a much more likely hypothesis.
Arboreal Archaeopteryx
There is a great deal of data to suggest that the archaeopteryx flew by launching itself from a tree branch or high cliff-top. Firstly, several papers, including Chatterjee (Chatterjee S. 1997. The rise of birds. Johns Hopkins University Press, Baltimore) and Feduccia and Tordoff (Feduccia A, Tordoff HB. 1979. Feathers of Archaeopteryx: asymmetric vanes indicate aerodynamic function. Science 203:10211022), point out that the animal, like modern birds, possessed a large cerebellum, a strong furcula providing effective support for the pectoral muscles, and other attributes that suggest flight capability. On the other hand, Archaeopteryx lacked the necessary anatomy for rotating the humerus, and further the structure of its wrist prevented it from beating its wings rapidly, making ground takeoff unlikely. In addition, study of fossils suggested that Archaeopteryx possessed feet which resembled those of modern climbing birds, such as woodpeckers. Therefore, the current consensus, after constructions of elaborate computer models and flight simulations, seems to be that Archaeopteryx launched itself into the air from the branches of its arboreal home, and moved about by gliding from tree to tree.
Additional Source:
Pat Shipman (1999). Taking Wing: Archaeopteryx and the Evolution of Bird Flight. Simon & Schuster. ISBN: 978-0684849652
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