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Re: Ceratopsian neck frills



>From: ornstn@hookup.net (Ronald Orenstein)
 > >[Note, except for Triceratops, the neck frill bones of ceratopsians
 > >have big holes in them, making then useless as shields, which
 > >leaves only display].
 > 
 > And, I would have thought, increased area for the atachment of adductor
 > muscles of the jaw;  I would be astonished if these areas in life were not
 > covered with tendinous material providing surfaces for the origin of muscle
 > fibres, prbably on both sides. 

Of course they were.  I was making no statement about soft tissues,
that is why I specified "bones".  In fact the presence of soft tissues
makes the frills even *less* useful as a shield, as such tissues would
be prone to serious injury in the process.

I have certainly seen it argued that the frills provided attachment
points for jaw muscles, and indeed they may well have done so.
But the shapes and marginal structures of the frills, and especially
the great variation in these features, cannot be related to functional
considerations.  From the trapezoidal frill of Chasmosaurus to the
small, heavily spiked frill of Styracosaurus, the shapes are very
prominant, and thus appropriate for display purposes.  A purely
mechanical frill would be more like that of "Monoclonius": small,
simple, and robust.

 > This sort of setup makes for a lighter skull
 > without losing areas of origin; perhaps the short frill of Triceraops
 > obviated the need for this?

Even the other short frills had holes in the bone.  In fact the
Triceratops skull is one of the heaviest skulls of any land animal.
[It is possible that Torosaurus or Pentaceratops might have had a
heavier skull].

And no matter how you look at it, the spikes on the frill of
Styracosaurus are clearly display structures.
 > 
 > Anyway, I would think that even a frill with large fenestrae could serve to
 > protect the neck from an attack from above; it would be that much harder to
 > get a killing grip on the back of the neck (assuming that the predators on
 > ceratopians killed their prey in this way).

But in the process of doing so, it would suffer serious injury.
This is not an effective way of protecting an animal.  Also,
given the jaw and tooth structure of tyrannosaurs, it is unlikely
they used the neck grip to kill thier prey anyway - that is largely
a mammalian specialty.

My guess is that the frill *originated* as a jaw muscle attachment
(in the protoceratopsids), and then got elaborated into the wide
range of larger, more complex, more varied structures of the
ceratopsids as a display structure.

swf@elsegundoca.attgis.com              sarima@netcom.com

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