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Re: Therizanosaurs and Cladistics



Stang1996@aol.com wrote: 

    >In any case, I am still a little reserved at calling these beasts
>theropods (that tetradactyl pes still has a _lot_ of explaining), but the
>idea isn't quite as absurd as I otiginally thought it to be when Thom Holtz
>started his whole _Alxasaurus_ kick a few months ago.

  Actually, the tetradactyl foot isn't incompatible with the theropod
clade.  All theropods have 4 toes.  Most birds (flying theropods) have four
functional toes.  Some (such as the ostrich) have two functional toes.
Most non-avian theropods (such as T. rex) have 4 toes, with three of which 
contact the ground.  The other toe is situated high on the foot,
behind the 3 other toes.  It seems a little counter-intuitive to call a
dinosaur with four toes contacting the ground a theropod, but there is
nothing wrong in the cladistic sense by doing so. 
  From a "Linnaean point of view", on the other hand, having four toes in
contact with the ground MAY be reason-enough to put it in another group....
... but of course, since Linnaean systematics is EXTREMELY opinion-based,
it will depend on which Linnaean systematicist you ask. 

  >  My vote for diet is herbivore.  This is because of the teeth, and it's
>not especially preditory demeaner (not especcially fast, small head, giant
>gut).

  You might be right.  But that doesn't preclude the possibility that it is
still a theropod. 

>    In any case I will be (in the days to follow, maybe today) sending y'all
> my family tree of dinosaurs as I see it.  I will attempt to send you two
>trees, one linnean, the other cladistic.

Actually, you'll be sending us *one* tree. The other is a hierarchial grouping.
Cladistics is a "family tree" of sorts.  But Linnaean systematics 
is nothing more than putting name-labels on organisms.  No 
family-tree is implied in Linnaean systematics.