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Re: A fundimental conundrum concerning gigantic theropods



In a message dated 96-11-08 12:44:55 EST, meyersrt@uwec.edu (Rob Meyerson)
writes:

> Further, being quadrepedal has a disadvantage in terms of being a high
> speed creature, in that the front limbs get in the way.  When a
> cheetah is running, all it's forward thrust is provided by the hind
> limbs.  The front limbs do little more than keep up and provide
> steering.  One could almost say that the front limbs slow the animal
> down, preventing it from getting to the maximum velocity possible.  As
> a result, it is a speed advantage to get one's front limbs out of the
> way by converting to a bipedal mode.

Then why are the fastest extant terrestrial animals all quadrupeds? Gazelles,
antelope, and cheetahs beat ostriches and smaller running birds and kangaroos
for sure. This business about bipedality evolving >as an adaptation for
increased speed< is too simplistic. Gotta look at physiology, stance,
behavior, everything, not just speed. Almost all extant bipeds are highly
derived animals with long evolutionary histories in which their bipedal
stance has been exapted for all kinds of purposes, including but not limited
to high-speed running. The question is, Why did they get up on their hind
legs the >first< time? Maybe just to have a look around, or to intimidate a
rival, or to mate, or to climb a tree. No way to choose among lots of
plausible alternatives.