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RE: Oviraptorosaur tail forms and functions

> Date: Thu, 10 Jan 2013 15:55:24 +1100
> From: tijawi@gmail.com
> To: dinosaur@usc.edu
> Subject: Re: Oviraptorosaur tail forms and functions
> Michael Habib <biologyinmotion@gmail.com> wrote:
> > I see what you're getting at, but do we really have a good threshold for
> > being "over-engineered"? Why can't a muscular, mobile tail basically just
> > be a display structure?
> It may well be just be a display structure. I hope it is the case
> that large oviraptorosaurs sported large and elaborate "fans". My
> argument (such as it is) is that the evidence is not compelling - at
> least as far as derived oviraptorosaurs are concerned. Across
> non-ornithuromorph theropods, there is no correlation between the
> presence of a pygostyle and a tail "fan" (= a radial arrangement of
> feathers).

I would think that oviraptorosaurs wouldn't need a large fan-tail...as their 
heads already make an ideal display structure.   (On the other hand, having the 
head and a fan-tail both being display structures, might provide the same sort 
of advantage that eyespots and false heads serve in fish and reptiles)

> Many non-ornithuromorph birds (confuciusornithids, several
> enantiornitheans) have a pygostyle, but no tail fan - although they do
> show terminal feathers (often streamer-like) that appear to have been
> used for display, associated with the pygostyle.

Perhaps additional comparisons are needed?  You mentioned three groups within 
the Therapoda who have a pygostyle - does the feature appear outside the 
(from what I remember last I saw a specimen in a museum, ankylosaurs have a 
similar-looking structure in their own tails; yes/no?)