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RE: Talluscoatum and Maniraptoran Tyrannosaurs



-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of Nicholas Gardner
 
>Below is my rather early and tenative classification of Maniraptora (Passer + Enigmosaurus) 
 
Nooooooooooooooooooooooooooooooooooooo!!!!!!!!!!!!!!!!!
 
Maniraptora suffers from "too many definitions syndrome" anyway.  Gauthier was explicit in his original definition in 1986: its modern birds and all taxa closer to them than to ornithomimosaurs.  My 1994 "redefinition" was unwarrented: hence the creation in 1996 of Maniraptoriformes.  Sereno's 1997/1998 "redefinition" (modern birds + Oviraptor) is equally unwarrented
 
>that includes tyrannosaurs.  Yes, I know it needs work and probably should be revised, but I thought I would get
>opinions on it.
 
--Maniraptora
  |--"Enigmosauria" Keesey, unofficial
  |  |--Oviraptorosauria
  |  |  |?-Caudipteryx
  |  |  `--+--Avimimidae
  |  |     `--Oviraptoroidea
  |  |        |--Elmisauridae
  |  |        |  `--+--Microvenator
  |  |        |     `--(others)
  |  |        `--Oviraptoridae (sensu J.A. Headden, DML)
  |  `--Therizinosauria
  |     |?-Beipiaosaurus
  |     `--Therizinosauroidea
  |        |?-Alxasaurus
  |        `--Therizinosauridae
  |           |?-Nothronychus
  |           |--Segnosaurinae (?=Enigmosaurinae)
  |           |  |--Enigmosaurus
  |           |  |--Erlikosaurus
  |           |  `--Segnosaurus
  |           `--Therizinosaurinae
  |              |--Nanshiungosaurus
  |              `--Therizinosaurus
  `--Eumaniraptora
     |--+--Aves ==(1)
     |  |  |?-Alvarezsauridae
     |  |  `---->Pygostylia
     |  `--Dromaeosauroidea (implied Matthew & Brown, 1922)
     |     |--Archaeopterygidae
     |     |  |--Archaeopteryx
     |     |  `--Rahonavinae
     |     |     |--Rahonavis
     |     |     `?-Vorona
     |     `---->Dromaeosauridae
     `--+==(2)
        |?-Ornitholestidae + Coelurus
        `---->Tyrannosauroidea
 
 
>1) hyperextendable toe lost after dromey/bird split
>2) hyperextendable toe secondarily reduced and (?)lost in tyrannosaurs; L-shaped cannon bone of the foot; and the
>T-shaped bone of the jugal region (I can't remember what the specific bone is called but it was used to unite the
>tyrannosaurs with the ornitholestians and the allosaurs)
 
My primary comment is that despite the presentation of the above as a cladogram, what you are dealing with here is the pre-cladistic model of phylogeny reconstruction. That method was based largely on the confirmation bias: you extol the "hits" and ignore the "misses".  In other words, you cite a small handful of features that support your hypothesis, but do not deal with those which refute it (although, to be fair, you do deal with the absence of the hyperextendable toe in tyrannosaurs (where it is most assuredly NOT present!!!!).
 
Of minor note, Vorona was established as a much more derived bird than the archaeopterygids, so other than their co-occurrance in the same quarry there is little shared between them among the birds.
 
Of major note, I can think of almost no features found in Ornitholestes, Coelurus, and tyrannosauroids shared with the eumaniraptorans that are not also shared with "enigmosaurs".  In contrast, nearly every paleontologist whose worked on theropod phylogeny for the last 15 years has found numerous features shared by "enigmosaurs" and eumaniraptorans that are not present in tyrannosauroids and other basal coelurosaurs.
 
I am interested in your reasons for placing Microvenator in Elmisauridae (more properly Caenagnathidae).
 
If you popped the tyrannosauroids and coelurid-grade forms out of there, I'd largerly agree with the details.  However, I think that troodontids would definitely be up in there.
 
>As I said above it is very tenative and is in need of revision.  The Ornitholestes + Tyrannosauroidea clade may
>need to include the ornithomimosaurs but that would mean the ornithomimes lost their semi-lunate carpals
>secondarily.
 
Ummmm...  Gee, I wish I had thought of that... :-)  (Holtz, 1994).
 
>Perhaps the ornithomimes
>re-expanded their carpals to brace the manus.  That would be important if they were using their hands as rakes
>and/or defensive weapons.
 
You are mistaken about the wrist morphology of ornithomimosaurs.  Their carpals are NOT re-expanded: they are instead reduced relative to the condition in typical theropods OR more derived maniraptorans.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742      
http://www.geol.umd.edu/~tholtz/tholtz.htm
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