Archaeopteryx Archaeopteryx Archaeopteryx (), meaning "old wing" (sometimes referred to by its German name ("original bird" or "first bird")), is a genus of bird-like dinosaurs that is transitional between non-avian feathered dinosaurs and modern birds. The name derives from the ancient Greek ("archaīos") meaning "ancient", and ("ptéryx"), meaning "feather" or "wing". Between the late nineteenth century and the early twenty-first century, "Archaeopteryx" had been generally accepted by palaeontologists and popular reference books as the oldest known bird (member of the group Avialae). Older potential avialans have since been identified, including "Anchiornis", "Xiaotingia", and "Aurornis". "Archaeopteryx" lived in the Late Jurassic around
Archaeopteryx be related particularly closely to "Anchiornis" and "Xiaotingia", which were recovered as basal troodontids instead. Agnolín and Novas (2013) found "Archaeopteryx" and (possibly synonymous) "Wellnhoferia" to be the basalmost avialans (Avialae being defined by the authors as including "Archaeopteryx lithographica" and "Passer", their most recent common ancestor and all of its descendants), with Microraptoria, Unenlagiinae, and the clade containing "Anchiornis" and "Xiaotingia" being successively closer outgroups to the Avialae. Another phylogenetic study by Godefroit, "et al.", using a more inclusive matrix than the one from the analysis in the description of "Eosinopteryx brevipenna", also found "Archaeopteryx" to be a member