Re: Megaraptor (was Re: Pygostyle)

[Oliver Rauhut <h2068d4p@rz.hu-berlin.de>]

On Thu, 23 Sep 1999 NJPharris@aol.com wrote:

> The foot of _Alvarezsaurus_ is rather like that of a dromaeosaur, with a 
> shortened MT II, inwardly-diverging pedal digit II, and laterally bowed MT 
> IV.  At least one recent analysis (can't remember whose, at the moment), 
> placed Alvarezsauridae just outside of (_Archaeopteryx_ + modern birds), a 
> position quite near that of the Dromaeosauridae.
> 
> So it is possible that the Alvarezsauridae arose from within or near the 
> Dromaeosauridae, and that _Megaraptor_, with its dromaeosaur-like pedal claw 
> and alvarezsaur-like forearm, is a basal alvarezsaur.

The analysis you mentioned was presented by Louis Chiappe at the Ostrom
Symposium. However, I wouldn't take it that far as to say that the
forelimb is alvarezsaur-like: the two known forelimb elements of
Magaraptor are very unlike those of Mononykus or Patagonykus; the only
similarity is the presence of a well developed olecranon process.
The morphology of the proximal end of the Megaraptor ulna is rather
unique, and consequently Novas used it to diagnose the taxon. As I said
earlier: we simply need more material to say anything about the
phylogenetic position of Megaraptor with any certainty.