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Re: late night thoughts: misunderstand what?

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. 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?

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. 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. 

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.

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?  L1,2,3,4 cannot possibly demonstrate an overarching size trend
under those conditions, even w/ perfect preservation. L1 runs from an enemy, 
get to 65 mph, get busted by the cops. Then L2 does the same. Does the fact L2 
didn't get busted at 70 mph, but still got popped at 65, mean it's not being 
chased? Or that L1 and L2 are not being chased by something
that can go faster than 65, and absolutely HAVE to get busted?

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

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?


----- Original Message ----
From: Andreas Johansson <andreasj@gmail.com>
To: dinosaur@usc.edu
Sent: Wednesday, June 20, 2007 4:18:34 AM
Subject: late night thoughts: misunderstand what?

On 6/18/07, don ohmes <d_ohmes@yahoo.com> wrote:
> ----- Original Message ----
> From: Andreas Johansson <andreasj@gmail.com>
> To: d_ohmes@yahoo.com; dinosaur@usc.edu
> Sent: Monday, June 18, 2007 5:57:06 AM
> Subject: Re: Fw: late night thoughts: misunderstand what?
> On 6/18/07, don ohmes <d_ohmes@yahoo.com> wrote:
> > AJ-- "Your idea need to be anchored in actual spatiotemporal distributions 
> > of fossils."
> >
> > They are. Sauropods and theropods both appear in the Late Triassic aka 'the 
> > beginning'. They coexist until KPg... aka 'the end'.
> You said that the largest thero's and sauro's occured simultaneously.
> Retreating to that they both occured in the Late Triassic to end
> Cretaceous isn't merely stretching the idea of "simultaneously", it's
> cutting it in two.
> ------------ Come again? The largest occurred in the Triassic? I didn't say 
> that, and it is not the case.

You want to argue that thero's and sauro's were involved in a size
race. Simply stating that the biggest of each lived simultaneously or
that they coexisted throughout the Late Triassic to the end Cretaceous
isn't enough for that: you have to point to instances of thero and
sauro lineages that plausibly interacted with one another growing
larger in tandem.

> And your second sentence isn't clear to anyone I've showed it to... so??? -- 
> DO.

Very simple: you claimed that the biggest sauro's and thero's lived at
the same time, and when I asked you to specify when and where you said
they lived throughout the LTr to the KPg.

> > Our perspective on evolution is evidently very different. I don't think 
> > that the end theropod being the biggest, and the end sauropod being the 
> > most armored, and quite large, does anything to falsify the notion of a 
> > prey/predator size race.
> If prey not getting larger doesn't do anything to falsify the notion
> of a predator/prey size race, what on earth would?
> .............. Are you saying there was no thero/sauro size race and the 
> fossil record shows that?

If you are saying that there was *a* thero/sauro size race that went
on for the duration of their 150M-odd coexistence, I do say the fossil
record shows quite clearly that was not the case. If you're saying
there were some such races going on during shorter timespans involving
sublineages, I am merely asking you to provide examples where you
think that happened. I've also pointed out a specifc instance where it
didn't happen - tyrannosaurs vs. *Alamosaurus* and ilk.

> Also, prey not getting larger when? In general, or specific to the 
> thero/sauro case?

Not getting larger when the Tyrannosaurs got large. This is a
counterexample to your model of thero's and sauro's getting larger in

> I make every effort to be clear...

I am afraid your success has been mixed.

> I seem to be faced w/ the concept that if prey size does not increase to 
> infinity, or there is not total extinction of prey, then a size race has not 
> occurred, but I am not sure. -- DO.

Not at all. You are faced by a) the fact that thero's and sauro's did
not grow continuously larger across the Jurassic and Cretaceous, and
b) requests for specific examples where you think size races occured.

> > That T.rex evolved separately from the allosaurids seems indicative to me 
> > that the evolutionary sub-strate was conducive to creating mega-predators.
> Certainly, but an environment conducive to the evolution of
> mega-predators does not equal a size race between those mega-predators
> and mega-sauropods, especially not for those mega-predators that, as
> far as is known, did not coexist with mega-sauropods.
> .........Are you saying there was no thero/sauro size race and the fossil 
> record shows that?  -- DO.

See above.

Andreas Johansson

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