[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: "Cursoriality", etc.

> Date:          Fri, 26 Sep 1997 06:26:33 -0700
> Reply-to:      jwoolf@erinet.com
> From:          Jonathon Woolf <jwoolf@erinet.com>
> To:            GSP1954@aol.com
> Cc:            jrhutch@socrates.berkeley.edu, dinosaur@usc.edu
> Subject:       Re: "Cursoriality", etc.

> GSP1954@aol.com wrote:
> > 
> > In some ways is it actually easier to maintain a high speed as size
> > increases. 
> It takes more energy, more muscle power, to accelerate than to maintain
> a given speed, does it not?  Maybe a hadrosaur could cruise all day at
> 25mph, but how long would it take that hadrosaur to _reach_ 25mph? 
> Maybe a tyrannosaur could sustain 30mph for a week, but how long a run
> in open country would it need to reach 30mph?  You're talking about
> accelerating six or seven tons of meat and bone, after all.  That's a
> lot of mass, and it will take a lot of energy and time to accelerate.   

It doesn't take long for an elephant to hit its top speed of 25-30mph 
and it's accelerating up to 8+tons.  Why would a tyrannosaur be any 
different even though it is bipedal?
> Then there's the issue of musculature.  If a tyrannosaur had musculature
> like a cheetah -- HIGH energy output for a short time -- it wasn't going
> to get going very fast.  A cheetah can sustain its super-high energy
> output for ten or twenty seconds, enough to carry it to a speed of over
> 100kph and a distance of half a kilometer or so.  How fast could a
> tyrannosaur go if it could only sustain high energy output for thirty
> seconds?  Especially considering that anatomy notwithstanding, there are
> mechanical limits to how fast a leg can be physically picked up, swung
> forward, and put back down.

While cheetah have more red than white fibers (much more) they are 
limited not so much by their musculature, but by their ventilation 
and the build up of heat.  They do reach speeds of 60-70mph (?more) 
and can run for distances of 1.5 miles or more.  But then they must 
rest to ventilate off heat (they don't sweat) and restore O2 and get 
rid of CO2.  Tyrannosaur, IF they had avian ventilation, would have 
been_perhaps_more efficient in that regards.  

Some people 7-2 run better than those 5-6.  For the tyrannosaur, it 
means can the bones and joints take the stress and did it limit the 
weight in the distal end of the pendulum enough to move it rapidly 
enough to increase stride frequency.  If an 8 ton elephant can do it 
with what appears to be poor anatomy for "running" and is not a 
predator, then what could a tyrannosaur do?       
> Also, concerning these compraisons of dinosaurs to rhinos and
> titanotheres: doesn't it make sense that you may not be able to
> reasonably compare two-footed animals and four-footed animals? 

You're right.  Quadripedal is fast, but not that much faster than 
some bipedal.  Cheetah run 60-70 probably.  New data says spotted 
hyena can hit 60 (I still don't believe it, but the source is hard 
for me to argue with- How about that Dr. Holtz), but ostrich are 
45-60 (depends on the source) and how fast are kangaroo.  BTW, what 
dinosaurs locomoted if at all like kangaroo?