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what's the current thinking on ceratopsian frills?



        To wit, what were they for?  Growing up during the "great fossil
lizard" era, I read that they were protective in nature, to guard against
tyrannosaurs chomping their necks.  I don't hear that theory much anymore,
so I assume it's fallen out of favor.
        In the excellent book "The Horned Dinosaurs" (author slips my mind,
sorry), sexual display and/or species identification is hypothesized.  All
those spikes, knobs, and processes are supposed to have been analagous to
antlers on modern artiodactyls.  The author examines and refutes the idea
that the frills could have been anchors for heavy jaw muscles.  He says
that there would have been no clear path from the frill over the face and
cheekbones (what are those called?) to the jaws.  He does allow that the
fenestrae on frills in chasmosaurines and the like could have accomodated
some muscles, but not many.
        Another theory that seemed very plausible to me was offered by the
science writer and illustrator John C. McLoughlin in his book
"Archosauria".  He argued that the frills were there to anchor, not the jaw
muscles, but the neck muscles.  He said that the ceratopsians' heads were
growing so big and heavy that the frills gradually evolved and grew in size
in order to be able to accomodate the neck musculature.  The solid frills
of the triceratops and kin and the fenestrated frills of chasmosaurines
were two different evolutionary solutions to the same problem.  Seemed
logical to me, but I have never seen this idea seconded by anyone.  Nor
have I ever seen a ceratopsian reconstructed like this, other than by
McLoughlin.
        So, what were the frills for?  A precis of current thinking or a
pointer to some literature will be appreciated muchly.

bruce

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        "Dammit, Philbert; what kind of a lepidopterist are you?  For god's 
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