Archaeopteryx for flightless birds. In 2010, Robert L. Nudds and Gareth J. Dyke in the journal "Science" published a paper in which they analysed the rachises of the primary feathers of "Confuciusornis" and "Archaeopteryx". The analysis suggested that the rachises on these two genera were thinner and weaker than those of modern birds relative to body mass. The authors determined that "Archaeopteryx" and "Confuciusornis", were unable to use flapping flight. This study was criticized by Philip J. Currie and Luis Chiappe. Chiappe suggested that it is difficult to measure the rachises of fossilized feathers, and Currie speculated that "Archaeopteryx" and "Confuciusornis"
Specimens of Archaeopteryx skeleton of a feathered animal from the same lithographic shale deposits, which would later be known as the London specimen. Coincidentally, von Meyer proposed the name "Archaeopteryx lithographica" for the feather, but not for the skeleton. Therefore, the official name of the animal was originally linked to the single feather rather than any actual skeleton, and is formally considered the original holotype. Though 1860 is often the year named for the feather's discovery, there is no proof of this date, and some authors consider it more likely to have been found in 1861, as it seems reasonable that von Meyer's