Re: The Wild and Wacky *Carnotaurus*

["Steve Brusatte" <dinoland@lycos.com>]

On Mon, 23 Apr 2001 23:14:47  
 Jaime A. Headden wrote:
>               (or: "Boy, Are My Arms Tired...")
>
>  Sometimes if ecology doesn't work off the bat, or the puniest
>things seem inapplicable or lead to Lamarckian statements, or
>allometry doesn't seem to explain anything ... there's always
>biomechanics.
>
>  There are two questions: 1) what are the brow horns for, 2)
>and why are the arms so small?
>
>  Both can be explainable as sexual characteristics: 1) brow
>horns in extant animals are usually display devices or wrestling
>devices, as in cervids, and proposed for ceratopsids
>(Wellnhofer, 1993). Perhaps the style is reminiscent of bighorn
>sheep: there is a broad, flat surface on the forehead with
>dorsally-flat lateral horns that form a platform (conceivably
>you can have two male carnotaurs pressing their foreheads
>together in a sort of elephant-likeshoving match). Perhaps they
>interlocked and the style was deer-like, with twisting involved;
>displace the arrangement of the horns on one and you get a
>cantered head, with carnotaur #1 having the left horn above his
>opposite's right and the right horn below the opposite's left...
>
>  Display features are usually in a position to be seen. Someone
>brought up *Cryolophosaurus,* plus *Dilophosaurus*.... These are
>front and side-view examples, whereas the best display use for
>the dorsoventrally-compressed horns of carnotaurs is from the
>top, and they would not be particularly visible from other
>angles, especially from the side, in which the head itself is
>best viewed. Seems likely then that display isn't very viable.
>Not impossible, mind.

That person would have been me.  Obviously, the brow horns of Carnotaurus are 
dissimiar to the crests of Dilophosaurus, Monolophosaurus, and Cryolophosaurus, 
but they may have served a similar function.  I do agree that they are best 
viewed from the top (at least from the skulls and photos that I have seen), but 
that doesn't necessarily mean that they were not for display purposes.  

Perhaps the Carnotaurus mating position brought the female in position to see 
the top of the male Carnotaurus' head, exposing the horns.  This may be very 
far out there, but who knows.  

More than likely, the were used for a combination of display/male aggression.  
I would tend to say, only judging by my limited knowledge of the Carnotaurus 
skull, that a bighorn-sheep like style of head-butting (with horns and a flat 
surface that allowed for the heads of two animals to rest together) seems more 
feasible than the interlocking deer style.  However, I could be very wrong.  
How flat is the part of the Carnotaurus skull immediately around the horns?  I 
guess I'll have to consult my photos.

In my opinion, sexual dimorphism and sexual study is one of the most 
fascinating topics in dinosaur research today.  I finally received a copy of 
Dinosaur Systematics for my birthday today, and hope to find time to read it 
soon.  I'm 11 years late in getting the book, I guess...but I was only six when 
it was published.  

Steve

---
***************************************************************
Steve Brusatte-DINO LAND PALEONTOLOGY
SITE: http://www.geocities.com/stegob
ONLINE CLUB: http://clubs.yahoo.com/clubs/thedinolanddinosaurdigsite
WEBRING: http://home.wanadoo.nl/dinodata.net/
INTERNATIONAL LANGUAGE SITE: http://www.geocities.com/stegob/international.html
****************************************************************


Get 250 color business cards for FREE!
http://businesscards.lycos.com/vp/fastpath/