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Re: Triassic dinosaur evolution



> But being a better fighter in one-to-one fights does not
> make for a better
> competitor. For example, a bear can tear a wolf in pieces
> one-in-one, but
> the wolf, by not maintaining a "code of honor" and going in gangs can 
> remove
> bears from a resource. Something similar with hyaenas and
> lions. Competition is won in ecological terms when the population of both
> competitors increase, some shared, necessary resource starts to be 
> scarce, and one of the competitors is better in finding the scarce 
> resource or better tolerates its lack. Killing the competitor may
> help... in case you can get it!!

Right, but I am just questioning the merits of a Quadruped predator vs a 
Bipedal predator. It seems to me quadrupeds are good at keeping a low profile 
for surprise attacks (as cats excell at) - giving a potential advantage at 
obtaining the resource.
As noted, speed is comparable in both bauplans.
Co-operative behavior (wolf vs bear analogy) is unaffected by quad/bi.
If they are just as fast as each other, and quad is "stealthier", what 
advantage does being a biped give?
Use of the front limbs (doesn't seem to stop cats from using them)?
An advantage in a fight? 

> one should recognize in favor of *T. rex* that its sheer size is just an
> advange, as the bear and tigers have their own advantages. It´s no fair
> to remove *T rex*'s advantage as it is
> no fair to cut forepaws of the bear to make the match more
> comparable, forcing both participants to fight only with their teeth.
> When counting with the superior size many lines reached, dinosaurs have
> an advantage not seen in other taxa, so that *T. rex* would have 
> destroyed the largest carnivorous mammals ever existed,

I did not mean to imply specifically a Dinosaur vs mammal faceoff, just a 
comparison of the merits of bipeds vs quadrupeds.
True, dino's did get huge, but its worth noting the largest ones were 
quadrupeds, not bipeds.
Generically, I would think a quadrupedal predator would be able to grow larger 
than a Biped, and given the limbs of a T-rex, its obvious freeing the forelimbs 
was not a major factor in the effectiveness of a biped predator. 


M Baeker wrote:
> Probably all this is obvious to anyone here, but since noone is saying
> anything along this lines...

> Note that there is a crucial difference in the bauplan that makes a
> quadruped dinosaurian runner less like, if I understand things
> correctly: Somewhere in their evolutuion mammals changed their
> backbone movement from left/right to up/down. Thus a cheetah gets some
> part of its speed from this movement which was (please correct me if
> I'm wrong here) not available to theropods.

But Lizards and crocs and such get part of their speed from side to side motion 
- its my understanding the up and down flexing of the mammal spine's main 
advantage is that it aids in respiration.
But this motion of the spine argument imo gets farther away from the more 
generic quad/biped question.

Without anticipating freeing the forelimbs for flight(which makes them very 
succesful now) was there some other major difference between the two groups 
other than bipedalism that was supposed to have given dinosaurs the edge? 
(under the "ordained for success" view, and not the "dino's got lucky with an 
extinction event" view)