RE: Diplodocus: Return to the Swamps????

[Dann Pigdon <dannj@alphalink.com.au>]

On Tue, Dec 15th, 2009 at 4:45 AM, Michael Erickson <tehdinomahn@live.com> 
wrote:

> But... Why mud at all? Couldn't sauropods have favored bodies of water with 
> sand and/or gravel,
> rather than mud? You know, big sandy- or gravelly-shored lakes rather than 
> mucky bayous.

I have a hard time imagining sauropods submerging themselves in *anything*. 
Sucking breath 
through those long necks would have been hard enough at the best of times. 
Having additional 
pressure around the lungs wouldn't have improved things.

Of course, just because I can't imagine something doesn't mean it didn't 
happen. :-)


The 'power' of sauropod muscles has been mentioned as a way for them to 
bulldoze their way 
through (or out of) mud. Exactly how much muscular power would sauropods have 
had though? 
Most modern reconstructions have them with surprisingly little muscle mass for 
their size (forget 
those old 'chunky' sauropod toys). Here's a sort-of-modern (1980s?) GSP image:
http://scienceblogs.com/tetrapodzoology/Greg_Paul_high-browsing_sauropods.jpg

Muscles in organisms are a bit like rocket fuel in rockets; the more you have, 
the more you need 
just to move it's own weight. If modern sauropod muscle reconstructions are to 
go by, it would 
seem that many sauropods had enough muscle to get around (slowly) in optimal 
terrain conditions, 
but not a lot extra. It's not like they needed to jump, or propel themselves 
around at a gallop.

Another reason I think it unlikely that sauropods *prefered* swampy areas has 
to do with cost 
verses benefits. Sauropods had tiny mouths for their size, which would have 
restricted the amount 
they could eat per unit of time. This in turn would suggest metabolisms 
considerably lower than 
those found in other dinosaur lineages.

Modern elephants avoid steep terrain if possible, due to the fact that they 
burn %2500 more joules 
moving vertically 1m than they would moving horizontally the same distance. If 
you burn more 
joules finding food than that food then provides for you, then you starve to 
death. See:

Wall, J., I.Douglas-Hamilton & F.Vollrath "Elephants Avoid Costly 
Mountaineering". Current Biology 
18(14) (PDf is online at http://www.savetheelephants.org/publications.html )

Elephants almost certainly have higher metabolisms than sauropods, and much 
larger mouths 
capable of consuming biomass more quickly. Yet they avoid overly strenuous 
modes of transport 
(climbing slopes) where possible, as it's energetically wasteful. I imagine 
(there's that word again) 
that plowing through mud would require much more energy than walking up sloping 
ground 
(depending of course on the degree of slope). Would sauropods have been able to 
spare all that 
extra energy? Perhaps if it meant the difference between immediate 
life-or-death, but somehow I 
don't see them pushing their way through swamps (or even deep water) on a 
regular basis.

-- 
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Dann Pigdon
GIS / Archaeologist                Australian Dinosaurs
Melbourne, Australia               http://home.alphalink.com.au/~dannj
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