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Re: Holes in Frills



On Thu, 5 Dec 1996 gpb6845@msu.oscs.montana.edu wrote:

> Possibly, but if that's the case, it makes one wonder why Triceratops
> closed up it's fenestrae when it's frill was proportionally as big (if
> not bigger) than most Centrosaurines.  I happen to think GSP's
> assertations in Dinosaurs Past and Present II (and possibly elsewhere)
> that the jaw muscles of ceratopians probably extended to nearly the
> end of the frill and that the peculiar "tounges" of bone in
> Centrosaurus' (or Monoclonius' or Eucentrosaurus' or whatever the hell
> they call it now) frill

Nick Longrich wrote:

>       A while back I took a look at an AMNH Centrosaurus skull. I am 
> not an expert but I came away completely convinced that the 
> muscle-attachment hypothesis was wrong. The reason is that the spikes 
> looked just like the hornlets around the frill, and this would be very 
> puzzling if they supported muscle instead of horn. 
>       Also it seems strange that this feature, if highly functional, is 
> not found in more centrosaurines, centrosaurines seem to have been much 
> more consevervative in their general anatomy than they were with display 
> features. 
>       The frill in general may also have served the purpose of 
> protecting the neck from the bites of tyrannosaurs. Notice the heavy neck 
> armor seen in nodosaurs and ankylosaurs, which was more than likely not 
> used to protect against damage during intraspecific combat. There was an 
> asian ankylosaur ( it was at the Russian dinos exhibit; can't remember the 
> genus) which has taken its eight neck  spikes and fused them into a 
> massive pair of half-circular collars each  bearing four low, stout 
> spines. Neck armor may have been very important in the late Cretaceous.
 
The supratemporalfenestrae in Triceratops are relatively small. The 
area around the supratemporalfenestrae is smooth.
This could mean that the attachement of the jaw muscles was 
restricted to the area around the supratemporalfenestrae (Rieppel 
1981; Dodson & Currie 1990; Dodson 1993; Forster 1996).
It is very unlikely if not to say impossible, that the whole frill 
served as a muscle-attachment-area.
First of all increase in muscle length does not increase it's 
strength (Dodson 1993; Forster 1996), only increase in sophistication 
of the muscle-fibers could have this effect (Dodson 1993). This 
increase was in Triceratops not necessary because of its better 
eveolved mandibular-system (Ostrom 1964,1966).
Second the whole frill-surface is heavily vascularized. This is 
absolutely incompatible with muscle attachement (Dodson 1993, Forster 1996). 
Probably the frill was covered with thick skin (Dodson 1993, Dodson & Currie
1990) ventrally and dorsally.

Hope the myth  of muscle-attachment on the whole frill in Triceratops 
will die soon.

Martin Westmeier

BTW excuse my bad english.

References:
Dodson, P. (1993): Comparative Craniology of  the Ceratopsia. In: American
Journal of Science 293A, Pp 200-234.

Dodson, P. & Currie, P.J. (1990): Neoceratopsia. In: Weishampel, D.B.; Dodson,
P. & Osmolska, H.: The Dinosauria. Berkeley, Los Angeles, Oxford, 1990,
p. 593-618.

Forster, C.A. (1996): New information on the skull of  Triceratops. 
In: Journal of Vertebrate Paleontology 16 (2), p. 246-258.

Ostrom, J. H. (1964): A functional analysis of jaw mechanics in the dinosaur 
Triceratops. In: Postilla, Yale Peabody Museum 88, p. 1-35.

Ostrom, J. H. (1966): Functional Morphology and Evolution of the Ceratopsian
dinosaurs. In: Evolution 20, p. 290-308.

Rieppel, O. (1981): [Function of the frill of the Ceratopsia] (In 
german) . In: Reif, W.-E. (Hrsg.): Palaeontologische Kursbuecher, Band 1:
Funktionsmorphologie. Muenchen: Palaeontologische Gesellschaft (Selbstverlag),
p. 205-216.