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Threads - Paleoclimatology

On 26/4/2003, in response to a query from Kevin Phyland, Paul Williams wrote:

> I'm curious as to how the "homeothermic" dinosaur theorem came
> about in the first place.

I'm afraid I do not know who first suggested this. Certainly in the late 19th century the American Nathaniel Marsh was putting together giant sauropods accurately (from a modern viewpoint).

> There is still lots of evidence that organisms as big as, say,
> Brachiosaurus, spent considerable time in water (swamps
> etc...)...was that to cool down or just to eat, or both?
>
<snip>

I believe that most modern books have thrown out this idea.
My first dinosaur book was illustrated with the famous murals from the Peabody Museum. These showed swamp dwelling sauropods. Many people believed that the giant sauropods could not carry their own weight unsupported. Water seemed (at the time) to be a good way for the giants to support their weight. My thoughts are that if they entered a swamp, they would never emerge - such large creatures would likely become bogged and starve to death. I think that they would have avoided swampy areas like the plague.

I've since visited the Peabody. It was interesting to see that they had kept the old style mounting ideas intermixed with more recent action posed 'raptors'.

Gerald Cairnes added:

I am not an expert in this but simply exploring what I see are fairly obvious environmental factors at play.

On the question of cold bloodedness versus warm bloodedness I suspect that what we have are at least two different strategies open to all complex living animals and each strategy has it's benefits and weaknesses. Homeothermy has enormous benefits but it carries a heavy energy cost while being cold blooded is a lot less energy intensive and in warmer climates this is very efficient. Then again being cold blooded allows you to see out the severe cold periods with a minuscule energy budget but it has the
disadvantage that they spend a significant part of the year torpid. Hibernating mammals do this also.

I imagine that Brachiosaurus in hot climates, homeothermic or not, did have problems with heat gain and like elephants would seek water where there also happens to be submerged grazing available. If they were homeothermic then they could extend their range of grazing which was probably a necessity judging by the sheer volume of their food intake that would have denuded local areas quickly if they were to stay around for long.

Large animals like elephant cannot lie down for long as as their weight will cause serious internal damage therefore I suspect that these very large dinos also had no choice but to keep moving day and night. There is no doubt though that a "composting" heap the size of their digestive systems would have produced a lot of heat which begs the question how did they shed excess heat other than by immersion in water? The physical shape of the animals would tend to make panting ineffective as a heat loss mechanism, did they sweat, probably not, did they manage their heat load by limiting their intake and minimising energy expended?

and

I don't think this swamp/land dwelling issue is an either or situation. I would be surprised if, as in modern times, that some animals did not become bogged in swamps and not all lakes would necessarily have had deep beds of mud but some may well have had sandy and quite firm foundations or at least firm enough not to be a hazard. I suspect also that periods of drought
would exacerbate this state.

In real life we tend to get a range of situations and environments with animals constantly exploring the limits.

I don't know about elephants either and not about to try but I can tell you that some horses insist on standing on toes, my bloody toes, and it hurts like hell! :-)

So....assuming an elephants foot is say 36 cm in diameter then the surface area of the foot print would be approx.. 2,036 sq. cm. Further assuming an average weight of say 3 tonnes divided by four = 0.75 tonnes per foot assuming an even distribution which is not correct as the front legs carry much more weight than the rear legs do. This equates to about 368 gm/sq. cm. That is a lot less than the average motor car "foot print".

Doesn't sound much but the bugger ain't gonna stand on my toes. :-))

Now more approximations. My foot is about 24 cm long by about 9 cm wide = 216 sq. cm
allowing for the shape of the foot multiply by say 0.75 = 162 sq. cm.
My weight is about 70 Kg so that is 35 kg per foot = 216 gm/sq. cm.

I make the elephant foot load at least 1.7 times my foot load, it's steel toe capped boots for me folks! Still it is an impressively low load for such a large animal.

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Warm Blooded Dinosaurs

Warm Blooded Dinosaurs