Re: Herrerasauridae

["Ken Kinman" <kinman@hotmail.com>]

     Cladistically it mainly depends on where you think the ornithischians 
split off relative to other dinosauromorphs.  Most workers believe 
Herrerasauridae are cladistically dinosaurs (i.e., probably split off after 
ornithischians).  Dinogeorge even hypothesizes that sauropodomorph clades 
split off first, before ornithischians, herrerasaurs, AND the lagosuchians 
as well.  This is the opposite of those who believe herrerasaurs are not 
dinosaurs (the other minority view).
     Unless we get a really extraordinary series of good fossils in this 
part of the tree, this arguing and uncertainty could last for many, many 
years (even decades).  Therefore, I begin the "dinosaur" clade at the base 
of the dinosauromorphs, but still maintain the traditional two orders of 
dinosaurs with the following topology (sauropodomorph taxa omitted for 
clarity):
SAURISCHIFORMES
   1  Lagerpetonidae
   2  Lagosuchidae
   3  Plesion Lewisuchus
   4  {{Ornithischiformes}}
   5  Herrerasauridae
   6  Plesion Eoraptor
   7  Plesion Saturnalia ...
   B    and other sauropodomorph taxa
   C    ...
   8  Guaibasauridae
   9  Coelophysidae
  10  Ceratosauridae ....
        and the rest of theropods

NOTE:  This topology makes Herrerasauridae cladistically dinosaurs (which is 
the majority viewpoint).  Future evidence may require that I change the 
topology (splitting order), but I think this is a pretty stable 
classification.  The same classification could be recoded to reflect many 
different alternate topologies, including Dinogeorge's (which would show 
various sauropodomorph clades splitting off first).  Anyway, for me this 
kind of classification makes all the different proposed topologies easier to 
comprehend.
           ------- Ken Kinman
*****************************************
Aspidel wrote:
> From: "Jean-michel BENOIT"
>
> > On his ( interesting ) site HP Øyvind M. Padron [gorgosaur@hotmail.com] 
> places the Herrerasauridae within dinosauria. I thought they had been moved 
> out somwhere between dinosauriforms and dinosauria?
>
> I asked the same question about _Chindesaurus_ in october, see HP David's
> reply:
> http://www.cmnh.org/fun/dinosaur-archive/2001Oct/msg00745.html ; see also
> http://www.cmnh.org/fun/dinosaur-archive/1998Nov/msg00532.html
>
> Is there something new now?



_________________________________________________________________
MSN Photos is the easiest way to share and print your photos: 
http://photos.msn.com/support/worldwide.aspx