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Re: THERMOREGULATORY FRILL



Here's one worthy of my steel;

> Fans of _Triceratops_: _Triceratops_ had three horns and a 'frill',
> or frilly collar. The point of the horns is easy to understand, but
> why the frill? To attract the opposite sex? Unlikely; such displays
> in nature are usually confined to the males, whereas both male and
> female _Triceratops_ have a frill.

Irrelevant.  Many artiodactyl species have horns in both genders, where the
 males simply have a better developed set (yes, they are hornier than the
 females).  Although determining gender in ceratopians is dicey at best,
 those "species" which are now considered to be females (_Chasmosaurus
 belli_, for example) seem to follow this pattern with frills and horns that
 are not as well developed as their male counterparts.

>Extra protection (i.e. extra to the horns)? Unlikely again; although
>made of bone, the frill is weakened by being full of holes. _The
>Economist_ (25 November 1995) quotes Reese Barrick 'a clever young
>man from Carolina', as regarding the _Triceratops_ frill as a
>heat-emitting device - a radiator. The large holes in the frill are
>apparently to reduce the weight and hence pressure on the neck.

[buzzing sound]
Wrong, try again.  Mr. Barrick has convieniently forgotted the jaw muscles
 that extended up into those holes.

As long as we are on the subject of frill jaw muscles, does anyone know if
 T-tops had a set of jaw muscles that extended to the top of the frill
 (heck, was there any muscle up there)?  I know that the main jaw muscles
 are held within and underneath the frill, but what about on the outside?
 Just idle curiosity on my part.

>The small ones, however, are to allow the passage of blood, thus
>distributing heat and allowing it to radiate away. The 'proof' of
>the radiator theory comes from oxygen isotopes. O-18 preferentially
>seeks cold sites; O-16 goes towards warmer ones. The horns have high
>O-18 (cold) and the body bones have high O-16 (warm), but the frill
>has high O-16 in the centre and high O-18 on the outside, indicating
>a 10 degree temperature differential between centre and
>outside. Just what you'd expect from a radiator.

Oy vey!  Oxegen ratios do not determine whether or not something will make a
 good radiator or not.  The real key is having a high surface area/volume
 ratio.  In that sense, the frill is a very poor radiator.

The frill-as-a-radiator hypothesis is a red herring.

Rob Meyerson
Orphan Vertebrate Paleontologist

***
"If anything is going to go wrong, it'll happen at maximum velocity."
                        -Red Green