RE: Feduccia in _PNAS_

[Tim Williams <twilliams_alpha@hotmail.com>]

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