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RE: Feduccia in _PNAS_

Christopher Taylor wrote:

AT the risk of a little pedantry, Clarke and Norell suggested that some of the characters usually regarded as 'enantiornithine' might be more widespread among basal birds. So, while they probably didn't doubt the monophyly of the main Enantiornithes clade, they did object to less
well-known species being assigned to Enantiornithes by a few 'signature' characters without an explicit phylogenetic analysis.

Well... in Clarke and Norell's own words:

"While 27 characters have been proposed as derived morphologies of Enantiornithes (e.g., Walker, 1981; Chiappe, 1991, 1996, 2001; Kurochkin, 1996; Sereno et al., 2002; listed in the supplementary information of Norell and Clarke, 2001), in the current analysis, only 4 characters support monophyly in both most parsimonious trees. The strict consensus of these is presented in figure 24. Enantiornithine monophyly collapses with a tree length one step longer than the most parsimonious topologies."

Given that Clarke and Norell used four fairly representative taxa (_Gobipteryx_, _Neuquenornis_, _Concornis_, _Cathayornis_) for Enantiornithes in their analysis, even the monophyly of a 'main Enantiornithes clade' seems shaky - at least according to that analysis. Also, Sereno (2005) defined Enantiornithes as the most inclusive clade containing _Sinornis santensis_ but not _Passer domesticus_. This is perhaps not the ideal definition of Enantiornithes, given that the eponymous taxon (_Enantiornis_) is excluded from the definition. Nevertheless the monophyly and/or composition of Enantiornithes hinges on the position of _Sinornis_ under this definition.