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Re: Oviraptorosaur tail forms and functions



I sent a query to the list that may have been lost in truncation:  is it 
possible that the tail did serve an "aerodynamic" function, or at least a 
stabilizing function in running (perhaps to make balancing or banking 
adjustments during rapid twists and turns), rather than for defense or display 
(though of course a colourful tail fan could still have a display function)?

Ronald Orenstein
1825 Shady Creek Court
Mississauga, ON L5L 3W2
Canada
ronorenstein.blogspot.com


________________________________
From: Tim Williams <tijawi@gmail.com>
To: dinosaur@usc.edu 
Sent: Sunday, January 13, 2013 7:48:02 PM
Subject: Re: Oviraptorosaur tail forms and functions

Augusto Haro <augustoharo@gmail.com> wrote:


> -Tail shortening of the kind seen in these oviraptorosaurs is not what I
> would expect in an animal using the tail as defense.
> -Animals using tails to hit are generally not as long-legged or obligate
> bipeds as oviraptorosaurs, probably for the sake of stability while
> delivering the blow.


Yes, I have to admit that I don't place too much stock in the
tail-as-a-weapon hypothesis.  I envisioned the tail more as a last
resort during defense, deployed against a small predator that came too
close.  Or used against a rival male during close-range combat.  The
oviraptorosaur tail is not in the same league as, say, the tail of an
ankylosaur, or even _Shunosaurus_.  Not even close.


The forelimbs of oviraptorosaurs might have been used in the same way:
as defensive weapons at close range.  If oviraptorosaurs were
herbivores (and the recent _Yulong_ paper apparently reiterates this
hypothesis), then the "raptorial" hands were unlikely to be used for
predation.


> I think a pygostyle may alternatively represent a way to strenghten the
> delicate small distal tail vertebrae when tail shortening put these closer
> to the base of the tail, at which stronger forces occur and may be
> transmitted to the tip by connective tissues.


What you say is more along the lines of what I was aiming at: Distal
reinforcement of the cau
byproduct of tail shortening.
The same thing probably happened with birds (Avialae).  It was not
until fairly late in avialan evolution that the pygostyle was co-opted
for aerodynamic purposes.






Cheers

Tim