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RE: Feduccia in _PNAS_



Jaime A. Headden wrote:

Technically, the first dinosaur paper of the new year; congrats, Alan.

The irony is, Dr Feduccia would not see it as a *dinosaur* paper. :-)

Feduccia's commentary is not exactly reflective of the current state of paleornithology. The entire issue of the origin of Aves (i.e., its sister taxon) is swept under the carpet; and Feduccia focuses on the distinctiveness of enantiornithine and ornithurine birds, chiefly from a paleobiological standpoint.

Feduccia does include a cladogram (adapted from Zhou [2004]), which shows _Archaeopteryx_, _Jeholornis_, _Sapeornis_, and _Confuciusornis_ as successive outgroups to an Enantiornithes-Ornithurae dichotomy. There's no outgroup(s) to Aves, and the cladogram excludes (in Feduccia's own words) "the more problematic avian microraptors and flightless bird _Caudipteryx_." Of course, these taxa are only problematic if you regard them (as Feduccia does) as non-dinosaurian birds. Talk about making life difficult for yourself...

Neverthless, the text and the cladogram seem to suggest that Feduccia is leaning away from Martin's Sauriurae concept. At least, that's what I glean from this:

"He [Martin] included the enantiornithines along with _Archaeopteryx_ within a subclass Sauriuriae, as distinctive from the subclass Ornithurae, or birds of modern aspect. {The skull of Archaeopteryx is extremely similar to that of enantiornithines, particularly Cathayornis (Martin & Zhou, 1997}. Since then, archaic birds that do not fit clearly into a taxonomic group have been described, including the primitive beaked bird _Confuciusornis_, the seed-eating bird _Jeholornis_ (with only three small teeth in the lower jaw), and _Sapeornis_ (with no lower jaw teeth), thus bringing into question the exact position of _Archaeopteryx_. Nevertheless, with the present description of the ornithurine _Hongshanornis_, the evidence appears overwhelming that "Early Cretaceous bird evolution highlights a distinctive dichotomy between enantiornithines and ornithurines, the two major avian groups of the Mesozoic" (Zhou & Zhang, 2005; see also Fig. 1 [=Zhou's cladogram]), a proposal that has been only weakly contradicted by a taxon from the Late Cretaceous (Clarke & Norell, 2002), at a time when homoplasy may be at play."

Although I would go along with the idea that there was a major Enantiornithes-Ornithurae dichotomy, the rest of the last sentence is rubbish. Clarke and Norell used _Apsaravis_ to argue against the "transitional shorebird" hypothesis for the origin of Neornithes, and has little impact on the issue of an Enantiornithes-Ornithurae split (though the authors did suggest that the monophyly of Enantiorithes might be shakier than previously thought).

The commentary also contains this brave assertion: "To date, there is simply no evidence, either structural or biological, for the existence of any form of protofeather" (Feduccia, Lingham-Soliar, & Hinchliffe, 2005)." I would suppose, then, that feathers arose via a spontaneous act of creation?

Cheers

Tim