RE: Rauhut and Xu on Tugulusaurus and Phaedrolosaurus

[Tim Williams <twilliams_alpha@hotmail.com>]

Jaime Headden wrote:

> The authors consider the leg to be
> diagnostic and comparable to other species, establishing the new taxon
> *Xinjiangovenator parvus*. There are some problems I am having with this,
> however, including the establishment of taxa based on a single 
> autapomorphy, so
> I am taking a closer, critical look.

To play devil's advocate: What is wrong with establishing a taxon upon a 
single autapomorphy?  As long as a genus or species has ONE character that 
can be used to distinguish it from any other genus or species, it is valid 
in my book.  _Archaeopteryx_ has precious few autapomorphies (maybe only 
one), but it is indisputably a valid genus.

I would go further and say that, even in the apparent absence of 
autapomorphies, a unique combination of characters is enough to validate a 
genus or species.  For example, Rauhut recently upheld _Genyodectes_ as a 
valid genus based upon the unique combination of characters displayed by the 
jaw material, even though it had no autapomorphies.

BTW, I enjoyed these summaries of _Tugulusaurus_ and _Xinjiangovenator_ - 
thanks Jaime.   I don't have much confidence that _Xinjiangovenator_ and 
_Bagaraatan_ form a separate clade of maniraptorans.  I wonder how both 
_Tugulusaurus_ and _Xinjiangovenator_ compare to _Yixianosaurus_?


Tim