 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 of Avialae (defined by the authors as the most inclusive clade containing Passer domesticus, but not Dromaeosaurus albertensis or Troodon formosus). Archaeopteryx was found to form a grade at the base of Avialae with Xiaotingia, Anchiornis, and Aurornis. Compared to Archaeopteryx, Xiaotingia was found to be more closely related to extant birds, while both Anchiornis and Aurornis were found to be more distantly so.
