Archaeopteryx airfoil. This would have reduced stall speed by up to 6% and turning radius by up to 12%. The feathers of "Archaeopteryx" were asymmetrical. This has been interpreted as evidence that it was a flyer, because flightless birds tend to have symmetrical feathers. Some scientists, including Thomson and Speakman, have questioned this. They studied more than 70 families of living birds, and found that some flightless types do have a range of asymmetry in their feathers, and that the feathers of "Archaeopteryx" fall into this range. The degree of asymmetry seen in "Archaeopteryx" is more typical for slow flyers than
Archaeopteryx common uses of that term. A more thorough analysis was published soon after to test this hypothesis, and failed to arrive at the same result; it found "Archaeopteryx" in its traditional position at the base of Avialae, while "Xiaotingia" was recovered as a basal dromaeosaurid or troodontid. The authors of the follow-up study noted that uncertainties still exist, and that it may not be possible to state confidently whether or not "Archaeopteryx" is a member of Avialae or not, barring new and better specimens of relevant species. Phylogenetic studies conducted by Senter, "et al." (2012) and Turner, Makovicky, and Norell