Re: Re[2]: new boook on functional morphology

[pharrinj@PLU.edu]

On Thu, 18 Jan 1996, Cunningham, Betty wrote:

>       So a ceratopian dinosaur would probably not do lots of weight 
>      shifting in order to go from it's standing posture to it's walking 
>      posture, as that tends to be more energy expensive.  

I don't think Mr. Orenstein meant to imply that ceratop(s)ids 
*habitually* adopted a sprawled resting posture; as I recall, he implied 
that the sprawled posture would be used to impart stability during 
intraspecific shoving matches.

>         If you had a multi-ton, 4 legged chicken (think of the drumsticks), 
>      it would probably be lazy as all get-out about this sort of thing.  
>      They stand, they walk, but they probably wouldn't do a splay-to-stand 
>      on a regular basis.  

Admittedly, it takes a lot of energy to stand erect.  However, as the 
ceratop couldn't rest on its belly like a croc or a lizard, it seems to 
me like it would be even *more* energy-intensive to stand around all day 
sprawling.

(In an erect limb, the weight of the body is transmitted 
passively to the ground, with muscular effort needed only to keep the 
bones in line; but if you stand in a sprawling position, you have to keep 
your triceps constantly flexed just to keep from collapsing.  Walking is 
a slightly different prospect.  Sprawlers are apparently a bit more 
energy-efficient when walking than are erect-legged animals.)

>      The leverage needed to make a splay become a 
>      tucked-under looks pretty awkward, but maybe they got special channels 
>      on the humerous and femur which could slide from one position to the 
>      other easier, I don't know.

I don't think anyone seriously suggested that ceratop(s)ians sprawled 
with their HIND legs.  There is absolutely no way they could do that.  
The head on the femur is at a right angle to the shaft, and if the dino 
tried to sprawl on it, it would have slipped right out of its socket.

That was always one of the weirder points of the sprawling ceratop 
theory:  The hindlimbs were supposed to be erect, but the forelimbs were 
supposed to sprawl.  Ceratop forelimbs are already considerably shorter 
than their hindlimbs, and sprawling would only have made matters worse.  
As Bakker pointed out in the _Dinosaur Heresies_, if such an animal 
had tried to go any faster than a shuffle, the back legs would quickly 
have overtaken the forelimbs, and it would have either 
gone around in circles (the back legs around the front) or flipped over 
altogether!

So what?  Maybe ceratop(s)ians just shuffled along slowly.  Well, there 
is the small matter of the hind legs, which are long and robust and show 
attachment points for very powerful muscles.  The ilium is very long, 
implying that the thigh muscles were enormous.  

The knees were quite flexible (in fact, as in many other 
dinosaurs, permanently flexed to some extent), and the hip joint could 
move through a wide arc.  If all the animal could manage was a slow 
shuffle, then what did it do with those immensely long and powerful hind 
legs??

>      
>      -Betty

Nick "sorry for the monster post, but this one is a real bugaboo of mine" 
Pharris