Re: Alwalkeria

["Mickey Mortimer" <Mickey_Mortimer111@msn.com>]

ekaterina A wrote-

> Is Alwalkeria considered a theropod or merely
> dinosauria incertae sedis? Has there been any recent
> redescription of it?

There's been no description since Chatterjee's original.  There's also been
little phylogenetic opinion excepting Paul's (1998; herrerasaur/protoavid)
and Chatterjee's (1987; coelophysoid).  To test its phylogenetic
relationships, I coded it in Rauhut's (2000) matrix.  7271 mpt's resulted,
with 656 steps each.  Alwalkeria had two equally parsimonious positions-
basal to Coelophysoidea + Averostra; sister group of coelophysoids except
Shuvosaurus.
Interestingly, Langer's (2001) topology of basal dinosaur relationships is
only four steps longer in Rauhut's matrix.  Enforcing this topology resulted
in 5112 mpt's of 660 steps each, where Alwalkeria appeared in the same two
positions.
Because Langer found Guaibasaurus to be in the same position Alwalkeria
sometimes appears in this analysis, I decided to add the former to Rauhut's
matrix as well.  Keeping Langer's topology enforced, Alwalkeria still comes
out in the same positions (10552 mpt's, 663 steps), though when basal to
coelophysoids, it is either more derived than Guaibasaurus, or its sister
group.
So, I recommend placing Alwalkeria as follows-
Saurischia
|--Herrerasauridae
`--+--Eoraptor
   `--Eusaurischia
      |--Sauropodomorpha
      `--Theropoda
         |--Guaibasaurus
         |-*Alwalkeria
         `--+--Coelophysoidea
            `--Averostra

Mickey Mortimer