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Re: late night thoughts: misunderstand what?

On 6/20/07, don ohmes <d_ohmes@yahoo.com> wrote:
You seem to be saying that for every large sauropod in the fossil
record, I must produce a large theropod of exactly the "predicted" size
and exactly the "predicted" age, or the concept of size race is invalid. The 
level of specific proof you require is not
now and never will be available from the fossil record, in my opinion.

That's not what I'm saying at all. I asking you to provide an example of co-occuring sauro and thero lineages increasing in size in tandem.

While I cannot prove they were there, a trip on my part to the time and place 
of Alamosaurus would entail preparations for an encounter with a large 
carnivorous biped. If you were going along for the ride, I think you would feel 
that wise, would you not?

Now you're not making any sense at all - *Tyrannosaurus rex*, the best known giant theropod bar none, is from that time and place. What's not known from that time and place is a seriously big *sauropod*.

By known ecological principles, evolutionary theory, and uniformintarian principles; showing that theropods and sauropods co-existed throughout their history, AND that valid predation scenarios exist, is indeed enough for me to argue, even assume, that they were in a size race, one that was continuous and operated on all the large lineages.

A continuous size race, by definition, means a continuous size increase. A continuous size increase did not occur. Ergo, there was no continuous size race.

This is elementary logic. Why is it so hard for you to understand?

I never said or thought that it was the ONLY size vector, that is not the way 
ecosystems work. In fact, the idea that standard top predator/top prey 
relationships was NOT a major driver of sauropod and theropod size is new to 
me, and I am sure to many other folks. But, as I am sure you have noticed I am 
out of touch. I wonder what you have to replace it.

Fallacy of the excluded middle. Rejecting a continuous 150+Ma size race 'tween thero's and sauro's does not imply rejecting top predator/prey relationships between them. Neither does it exclude that size races may have occured 'tween certain sub-lineages: this why I keep asking for instances of lineages growing in tandem.

I do not see that a 'ceiling' on size through the Jurassic/Cretaceous (taking 
everybody's word that it exists) invalidates such a bedrock ecological concept. 
I have always been a big fan of the idea that there are limits to size inherent 
to the laws of physics, and that these are modified downward by local 
conditions. It is one of my core assumptions.

Another of your core assumptions, it would seem, is that you can increase in size without getting bigger.

To repeat from last night, slightly edited: Here's what I don't understand 
about the 'take' on size trends.

Lineages 1,2,3,4,... recorded through time. Each gets big, hits an apparent 
ceiling (size limit), then sputters, dies.

does that negate predation as driver, and 'predators won" if the size
limit is real?

If the predators won, the sauropod lineages would go extinct an geological instant after hitting the ceiling; they couldn't "sputter", since, under your scenario, any sub-size descendants would get eaten even faster than those who merely failed to grow bigger.

Also, this really shouldn't need to be pointed out, but what you're
describing here isn't a continuous anything - it's a *dis*continuous

The "little" guys found refugia, possibly because large bipeds don't like soft 
ground. Or for a multitude of other reasons.

If the little guys where restricted to refugia, the smallish camarasaurs wouldn't be the most common sauropod fossils in the mega-thero'-infested Morrison formation, nor would saltasaurines be so common in the Late Cretaceous. The only reasonable conclusion is that the "little guys" were able to coexist with mega-thero's.

Which reminds me; how many of the smaller species have a long enough presence 
in the record to prove that they weren't also increasing in size?

Some no doubt did increase in size, but clearly some didn't, because we find small sauropods all the way from the Triassic to the end Cretaceous.

Andreas Johansson

Why can't you be a non-conformist just like everybody else?