Re: late night thoughts: misunderstand what?

[don ohmes <d_ohmes@yahoo.com>]

AJ -- "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."

A problem w/ the 'obligatory instant snuff out'  premise outlined above is 
this. If the taxa size variance begins to interact  w/ a mass size limit, the 
animals at the lower end of the variance, particularly those that live in 
habitats that contain areas of refugia, are less affected than those at the 
upper end of size variance. This process could take some time to play out, w/ 
unpredictable outcomes. Therefore, 'instant snuffout' is not predicted by a 
predator-driven size increase scenario. Sputtering can occur.

----- Original Message ----
From: Andreas Johansson <andreasj@gmail.com>
To: don ohmes <d_ohmes@yahoo.com>; dinosaur@usc.edu
Sent: Wednesday, June 20, 2007 9:38:56 AM
Subject: 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.
>
> How
> 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
process.

> 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?