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Re: Sloping terrain Re: Woman against Abelisaur



On 7/25/2011 3:00 AM, Tim Williams wrote:

As for the mired_Giraffatitan_, this is a different case altogether.
It's been suggested that it was driven to the lagoon in which it died
because of drought.

That camels have died of thirst in the desert does not imply that camels are out of their element in the desert.

Given an animal that spends a lot of time hip-deep in mud, one would certainly expect to occasionally find one preserved "in mired position" -- perhaps even having died as a result of miring. E.g. -- drought can change mud to virtual concrete, and the change can occur rapidly. Elephants sometimes become trapped in muddy pits that have steep slippery sides -- certainly their remains could be preserved in "mired position" -- and certainly they love mud, and are notably NOT hampered by their large size.

So finding an individual animal in "mired position" does not rule out (or in) much of anything, excepting that it does prove they at least one time entered such an environment.

In any case, were the somewhat circular assumptions underlying the 'driven-to-the-lagoon' scenario valid, I would expect many more mired sauropods to have been found, including multiple individuals preserved simultaneously -- especially given the increased chance of preservation relative to their more usual (within the "sauropods avoided soft seds" scenario) dry land placement.

> Larger individuals got stuck in the mud, but
smaller/lighter individuals could pull themselves out.

I think this interpretation is not the best fit.

The assumption that the disadvantage of weight overwhelms the advantages of absolute power, power relative to surface area, and leg length is not supported by observation of extant animals. Not supported by the physics either.

There can be special cases where a hard crust overlays softer seds, and lighter animals do not break through, AND the underlying seds are capable of trapping powerful animals, but such are rare in today's world -- given the large size of even the hypothetical "smaller/lighter individuals" in this case, it seems unlikely.

> The fact that
a large specimen of_Giraffatitan_  (and_Janenschia_  too) show limb
bones in an upright, articulated position indicates that they were
mired in the mud,

Possibly.

> and therefore implies they were in an environment
they weren't well suited to.

No. Penguins drown, camels die of thirst -- happens all the time.