RE: Pygostyle-like structure from Beipiaosaurus

["Tim Williams" <twilliams_alpha@hotmail.com>]

Thomas R. Holtz, Jr. wrote:

> >  Might this not be at least suggestive that (like kiwis and
> > moas, for example) this animal may have secondarily lost a more
> > complex set of epidermal tail structures?
>
> Indeed: that is, if it they really weren't present!  (Which they might have 
> been).

Has anyone considered the possibility that the development of a pygostyle 
was associated with *loss* of function, rather than the advent of some new 
function?  In other words, the development of pygostyles in _Nomingia_ and 
_Beipiaosaurus_ came about due to very different ecomorphological reasons 
than the development of a pygostyle in birds, and had nothing to do with its 
function in orniththoracine birds: support of the rectricial fan (used in 
flight or for display).

For example, truncation and coossification of the caudal vertebrae occurred 
because small maniraptorans no longer needed a long counterbalancing tail.  
Perhaps a long tail reduced the animal's agility when running, such as when 
negotiating sharp turns (Carrier et al., 2000).




Tim

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