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At 01:30 PM 4/8/99 GMT0BST, Darren Naish wrote:

>Whoops Nick, enantiornithines are emphatically not ornithurines and 
>never have been.

Depends on which definition of Ornithurae is used.  Following Gauthier
(1986) or Sereno (1998), Ornithurae is modern birds and all taxa closer to
them than to _Archaeopteryx_.  Enantiornithines almost certainly qualify
under that definition (unless Martin et al. are correct, and
enantiornithines are closer to Archie than to _Passer_).

However, using the definition followed by Chiappe, Padian et al., etc.,
Ornithurae is the node joining _Hesperornis_ and modern birds.  This
definition is closer to what Martin (1983 - in Brush & Clark's Perspectives
in Ornithology) and others have used in the past.  Enantiornithines are
almost certain outside of this clade.

Just one of those things that has to be worked out now...
>Working with empirical, rather than intuitive, data, other 
>palaeornithologists agree that Enantiornithes were a monophyletic 
>radiation of birds that represent the sister-group to ornithurines 
>(_Patagopteryx_, Hesperornithiformes, Ichthyornithiformes, 
>Neornithes) - this clade has been called Pygostylia. Pygostylia 
>+ _Iberomesornis_ is the clade Ornithothoraces. Confuciusornithids 
>are the sister-group to the Ornithothoraces (Ji et al. 1999).

The Padian et al. taxonomy defines Ornithothoraces as _Iberomesornis_ +
modern birds and all descendants of their most recent common ancestor;
Sereno uses _Sinornis_ instead of _Iberomesornis_.  However, some recent
studies (Kurochkin, 1996; papers in press by Sereno & by Chiappe, as
mentioned at the Ostrom Symposium) show _Iberomesornis_ to be an
enantiornithine.  Thus, although these definitions use different anchors,
they probably encompass precisely the same clades.

Oh, and with mention of the Sereno and Chiappe papers here, let me just note
that there will be a few pretty important reviews of enantiornithines
forthcoming in the next year or so.  [Token Holtz response #1, as per Josh
Smith ;-)  ]

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:tholtz@geol.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661