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Re: Lack of Running Giant Theropod Tracks



1) Sorry, Don, but you need to learn to cite literature correctly.
Henderson cited Dodson and others, so what you quoted was written
BEFORE Henderson's study. So you may actually be quoting something
Henderson REFUTED - the way you quote this is not clear.

2) to cite Bakker 1986: Hereford steers are found in the Gulf of
Mexiko. Doesn't make the aquatic. Don't mix taphonomy of large animals
with paleobiology.

3) the critical depths are calculated based on many assumptions, but
let's take the at face value. Diplodocus, 2.4 m. At that depth a large
predator would have to swim, but would easily be able to bite into the
tail that is floating on top of the water. OOPS.

4) you avoided the question what is supposed to replace the air? Will
the ribcage just cave, breaking the ribs? OOPS, no such fossils known.
You seem to claim that all assumed 15% of air get squeezed out -
please explain how the animals kept breathing.

5) as I had pointed out eariler, sauropods may have had as much as 40%
air. Even if you magically squeeze more than just half the
lung-related air sac volume out without collapsing the lung and
fragmenting the rib cage, they'd stay at somewhere near 30 percent.
Tipsy punters indeed. Henderson took a very un-buoyant version, he was
behind on the research. Check e.g., Matt Wedel's work:
http://sauroposeidon.wordpress.com/publications/

6) You seem to assume that a high COB is a good thing. However, the
more you shift it up, the more of the lung and air sacs is submerged,
and subjected to water pressure. OOPS again.....

7) Mike cited two papers by Alexander, you ignore both - why?




On Mon, Nov 29, 2010 at 7:46 PM, Don Ohmes <d_ohmes@yahoo.com> wrote:
> On 11/29/2010 11:48 AM, Heinrich Mallison wrote:
>
>> See, there really is no use talking to someone who makes up his own
>> version of physics as he goes along.
>
> Why bother to say things like that? I was going to take the rest of day
> out in my swamp...
>
>> On Mon, Nov 29, 2010 at 4:49 PM, Don Ohmes<d_ohmes@yahoo.com>  wrote:
>>
>>> It changes the center of buoyancy, at the least. In humans it changes
>>> buoyancy from positive to negative, and you sink. Try it in a swimming
>>> pool,
>>> but be careful.
>
>> in fact, the the motion of the center of buoyancy is totally irrelevant.
>
> It is irrelevant to humans sinking when they let their air out. I guess
> I should have started a new paragraph between the 1st and 2nd sentence.
>
>> The COB defines if you capsize.
>
> Which makes it's position relevant to the "tipsy punter" case, which you
> are attempting to use to rebut the "swampy sauropod scenario".
>
>> In sauropods its position and their body shape means that once
>> capsized they had practically no chance to get back onto their feet.
>> OOPS.
>
> Oops indeed, Heinrich. Read on --
>
> Decreasing the air volume in the body increases the density, which
> decreases the buoyancy. As external water pressure increases, is air not
> forced out of the body in the absence of a valve that holds it in, even
> in the unlikely absence of an ability to voluntarily deflate them?
>
> Is this air not moved out preferentially from bottom to top?
>
> Given that the air is mostly in the trunk, and the legs are dense,
> removing trunk air moves the cb up, increasing stability. Given that
> Henderson used an estimate of 15% air, this is significant.
>
> And certainly NOBODY claims that having their fortuitously compact feet
> buried in some mud will make them less stable!
>
> It is also worth noting that Henderson's model have the neck held erect
> and out of the water.
>
> In other words, Henderson has taken the most-buoyant, least stable case
> -- a case in which sauropods cannot voluntarily decrease air sac volume,
> or change the position of their necks. Which is alright, but should be
> noted as generally of interest.
>
> Please keep reading, Heinrich --
>
> Buoyancy is an irrelevant tangent to my central thesis about the binary
> aspect of the tactical balance between the mega-theropods and the
> sauropods -- that is because water so deep that all parties are buoyant
> seems likely to eliminate once again the sauropod's advantage in any case.
>
> Here is what Henderson says in the "Tipsy Punter" paper (emphasis added) --
>
> "The fossil remains of sauropods are known from coastal settings
> (Weishampel 1996), and are often found near to, or mixed in with,
> fossils of marine organisms (Allen 1975; Russell et al. 1980). These
> lines of evidence indicate that sauropods were not averse to moist
> conditions, and may have even preferred them (Dodson 1990).
>
> The interpretations presented here that sauropods could successfully
> walk in water that was ==> *at least!* <== as deep as their chest height
> are consistent with the association of sauropods and wet habitats."
>
> I hope you a) read the last paragraph carefully, and b) have a hanky
> handy. You have snark on your face...
>
> I supplement w/ critical depths equilibrium depths given by Henderson in
> the paper you apparently did not read --
>
> Critical depths: Apatosaurus, 3.7 m; Brachiosaurus, 4.3 m;
> Camarasaurus, 3.2 m; Diplodocus, 2.4 m.
>
>