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RE: Giant birds
> From: firstname.lastname@example.org [mailto:email@example.com]On Behalf Of
> Raymond Ancog
> I'm surprised at this. I would expect that troodontids + deinonychosaurs
> would be the sister group to Avialae, and then oviraptors and
> would be successive sister groups to the crown clade (based strictly on
> what I've read, not on first-hand information).
Sereno and Makovicky & Sues do find a troodontid + dromaeosaurid clade in
their analyses; however, I do not: troodontids come out as the sister taxon
to Ornithomimosauria OR the sister taxon to dromaeosaurids + birds. Xu et
al. (the _Sinornithosaurus_ paper) find the latter position, too. At the
Ostrom Symposium Norell presented an analysis by the AMNH staff: they found
troodontids as the sister taxon to oviraptorosaurs + therizinosauroids
(which is only one step longer than my most parsimonious trees in my
Or, as I've said to various people: troodontids suck! (at least
phylogenetically: have nothing against them personally...).
> Doesn't the
> enlarged second
> toe unite them to the exclusion of birds?
Actually, primitive birds (_Rahonavis_, for example) have an enlarged second
toe, and many primitive birds (_Rahonavis_, _Archaeopteryx_, some
enantiornithines) show hyperextensibility of pedal digit II.
> BTW, which is more acceptable, dromaeosaur or deinonychosaurs?
Both are acceptable: they represent different taxa. Dromaeosauridae is the
clade comprised of all descendants of the most recent common ancestor of
_Dromaeosaurus_ and _Velociraptor_; Deinonychosauria is the clade of all
taxa closer to _Deinonychus_ than to Neornithes. Under the Makovicky & Sues
or Sereno cladograms, troodontids are deinonychosaurs but not
dromaeosaurids; under the AMNH, Holtz, or Xu et al. cladograms the only
known deinonychosaurs are dromaeosaurids.
Thomas R. Holtz, Jr.
Department of Geology Director, Earth, Life & Time Program
University of Maryland College Park Scholars
College Park, MD 20742
Phone: 301-405-4084 Email: firstname.lastname@example.org
Fax (Geol): 301-314-9661 Fax (CPS-ELT): 301-314-7843