Ceratopsian Frills

["Richard W. Travsky" <rtravsky@uwyo.edu>]

Came across an article about horns in horned lizards and how they're
used in defense:

http://www.fieldherpers.com/genandsys/messages/2183.html

 ...the complete version with diagrams and citations is in Science, Vol
 304, Issue 5667, 65 , 2 April 2004

 How the Horned Lizard Got Its Horns
 Kevin V. Young,1 Edmund D. Brodie, Jr.,1 Edmund D. Brodie, III2*
 1 Department of Biology, Utah State University, Logan, UT 843225305, USA.
 2 Department of Biology, Indiana University, Bloomington, IN 474053700,
 USA 

 ...When shrikes attack horned lizards, they typically spear the lizard
 through the neck and pull off the soft tissue.

 ...The bony horns that give horned lizards their name are presumed to
 function as a defense against predators. Here we present data from the
 wild showing that natural selection by loggerhead shrikes favors longer
 horns in the flat-tailed horned lizard (Phrynosoma mcalli). 
 ...
 ...Our results showed predation by loggerhead shrikes generated selection
 that favored longer parietal and squamosal horns. The average parietal
 horn length of live horned lizards was 10.0% longer ... than that of
 shrike-killed lizards ...

(For those not familiar with what a horned lizard looks like, nice pic
and related article at
 http://www.sltrib.com/2004/Apr/04062004/tuesday/154456.asp  )

They don't quite describe how the horns are used, but two ways are
discernable, one, passively by simply offering a barrier to the shrike,
and second, by actively jerking the head back. 

It occurs to me that a ceratopsian frill employed actively could also be
effective. Given the weight of a frill and the strong neck muscles needed
to hold and move the head around, a sudden jerk back could deliver
considerable force against a predator going for the neck.