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Re: AVIMIMIDS & MANIRAPTORA SENSU HOLTZ



>MANIRAPTORA SENSU HOLTZ
>
>Gauthier originally defined maniraptorans as 'all coelurosaurs closer to birds
>than to ornithomimosaurs'. This was because he envisioned ornithomimosaurs
>diverging first right? The subsequent lineage, crowned by avialians, would
>therefore be the Maniraptora. Right? But Dr. Holtz' more recent analysis sees
>the dromaeosaurid + avialian clade diverging before the lineage including the
>ornithomimosaurs. This now means that all post - drom + avialian coelurosaurs
>are closer to ornithomimosaurs - it would therefore create a paraphyletic
>Maniraptora if we retained Gauthier's allocations. The Holtz solution to this
>was to redefine Maniraptora as the node shared by the drom + avialian clade and
>the clade including ornithomimosaurs (therefore ornithomimosaurs and
>tyrannosaurs are maniraptorans). Right? This effectively changes the definition
>of the maniraptorans entirely and, as revealed in a recent posting, Dr. Holtz
>now plans to amend this (Maniraptora would be the clade including droms and
>avialians, the node at which maniraptorans and later coelurosaurs diverged
>would
>now require a new name). BUT, in that definitive study, the new definition and
>allocation of the Maniraptora is stated clearly. Why must this be changed?
>Would
>people rather prefer Gauthier's original meaning of Maniraptora? Can someone
>tell me (sorry to be such a pain Dr. Holtz).

[Uh oh!  He caught me!!!  ;-) ]

My "redefintion" of Maniraptora Gauthier 1986 was entirely unwarrented.
Unfortunately, a few others have picked up on this (viz Clark et al. 1994).
You are quite correct - Gauthier's definition must stand.  The resolution
of this problem can be found in:

Holtz, T. R., Jr.  in press.  The phylogenetic taxonomy of the
Coelurosauria (Dinosauria: Theropoda).  Journal of Paleontology.

If the paper is not out by November, take a peak in the SVP abstracts
volume (supplement to issue 3) for a brief discussion of this.

                                
                 Thomas R. Holtz, Jr.                  Phone: 703-648-5280      
                 Vertebrate Paleontologist         Fax:    703-648-5420
tholtz@geochange.er.usgs.gov ------------>       th81@umail.umd.edu
U.S. Geological Survey          ------------->       University of Maryland
Branch of Paleontology & Stratigraphy ---->       Department of Geology
MS 970 National Center
Reston, VA  22092               ------------->        College Park, MD  20742
                                                          U.S.A.