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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 caudal series as a 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