Feathered dinosaur is possible that feathers first developed in an even earlier group, in light of the discovery of pycnofibers of pterosaurs. Crocodilians also possess beta keratin similar to those of birds, which suggests that they evolved from common ancestral genes. Shortly after the 1859 publication of Charles Darwin's "On the Origin of Species", British biologist Thomas Henry Huxley proposed that birds were descendants of dinosaurs. He compared the skeletal structure of "Compsognathus", a small theropod dinosaur, and the 'first bird' "Archaeopteryx lithographica" (both of which were found in the Upper Jurassic Bavarian limestone of Solnhofen). He showed that, apart from its
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