[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Re: new boook on functional morphology
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
(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
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
Nick "sorry for the monster post, but this one is a real bugaboo of mine"