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Segnosaurs are Theropods?



    I have never liked the idea of the Segnosauria being placed within 
in the Theropoda.  The many features that they share with the 
prosauropoda are convincing enough to conclude that they cannot be 
excluded as ancestors.  Also, after having veiwed the original type 
specimen of _Alxasaurus_, and looking for the supposed semi-lunate 
carpal block which is the seamingly only thing that links segnosaurs 
to theropods, I have to say that none of _Alxasaurus'_ wrist bones 
look especially like (or anything like for that matter) the obvious and 
distinctive semi-lunate carpal block of maniraptoran theropods.
    In "The Dinosauria", Barsbold and Maryan'ska listed a group of 
features that the segnosauria supposedly share with theropods 
alone:

1) A lack of a process of the dentary passing dorsal to the external 
mandibular fenestra.
  -This is not a feature that is possesed by all theropods, but it is     
    possesed by other dinosaurs as well.
2) Presence of pleurocoels in the vertibrae.
  -Sauropods have pleurocoelus vertibrae
3) The fibula closely appressed to the tibia.
  -The shinbones of segnosaurs are Very strange and bear no close   
   resemblance to any other dinosaur group; that the bones are close
   proves nothing.
4) Expanded pubic boot.
   -_Nanshiungosaurus_ does not have a booted pubis.
5) A tall ascending process of the astragulus.
   -Other dinosaurs have tall astraguli.

    There are however, many features that segnosaurs share with 
prosauropods, such as:

1) A relatively large premaxillary (compaired to theropods).
2) Elongate vomers.
3) Elongate nares.
4) Deep narial shelf.
5) Deeply recessed anteorbital fossa and fenestra.
6) Downwardly deflected dentary.
7) General tooth structure.
8) Broad tetradactyl pes (which George Olshevsky quite convincingly 
    shows is not a "reversion").
9) "T" -shaped postorbital.
10) "S" -shaped quadrate.
11) Low occiput.
12) Prearticular running the whole lower and forward margin of the     
    external mandibular fenestra.
14) The Prearticular-Angular-Splenial complex.
15) General hand structure and articulation.
16) Depressed jaw joint and a small "coronoid" process.
17) Lack of the maniraptoran "pulley-action" elbow-wrist complex 
   (i.e. the arms don't fold like birds').
18) Lack of the Avetheropodan "double-jointed" lower jaw.

With Ornithischians they share:

1) An opisthopubic pelvis.
2) General tooth structure (as per primitive forms).
3) Cheeks
4) Downwardly deflected Dentary.
5) Broad tetradactyl pes.
6) Hand articulation (as per _Heterodontosaurus_).
7) Depressed jaw joint and small "coronoid" process.
8) Lack of the maniraptoran "pulley-action" elbow-wrist complex.
9) Lack of the Avetheropodan "double-jointed" lower jaw.

  When I went to Vancouver and saw the type material of 
_Alxasaurus_ I was very excited.  I did not know it was going to be at 
the dinosaur exhibit at The Forum.  When I looked at the hand I really 
wanted to see the semi-lunate carpal block that "proves" its theropod 
affinities.  I looked and looked and stared ito a small plexiglass box 
for upwards of fifteen minutes looking for the semi-lunate carpal 
block.  I still cannot find it (yes, I know what a semi-lunate carpal 
block looks like).  I did take a picture of it and I am still looking for it.

 Please tell me where it's supposed to be!
    These are the many reasons I believe that Segnosaurs (not 
Therizanosauroideans) were transitional between prosauropods and 
ornithischians and not theropods.
    I know this will get responses.

Peter "I really couldn't see the semi-lunate carpal block!" Buchholz
Stang1996@aol.com

--Boycot Taco Bell's "Texas Tacos" and "Border Light" menu items.