[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Fw: late night thoughts: misunderstand what?

AJ-- "Your idea need to be anchored in actual spatiotemporal distributions of 

They are. Sauropods and theropods both appear in the Late Triassic aka 'the 
beginning'. They coexist until KPg... aka 'the end'. I think we are assuming 
different margins of error. My assumptions are quite large. It boils down to 
the probability of a given individual organism being both preserved and found, 
something that varies according to lifestyle and environment. I think that 
combined probability for terrestrial vertebrates is very, very, very low. 
Finding one individual in a given location indicates a long presence on the 
planet and says little about real geographical distribution.

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. From what you (and others) say, that was the 
situation. That T.rex evolved separately from the allosaurids seems indicative 
to me that the evolutionary sub-strate was conducive to creating 
mega-predators. Why would I conclude that sauropods weren't a part of that? 
While I can't be certain they were, it seems to attain best 'guess status'. Any 
small-ish predator in a sauropod-rich environment would exploit juveniles; from 
there the way to size increase is clear, in the selective sense. At some point 
the predator begins to pressure adults. Any other large herbivore would also 
fill the bill; the concept of predator-driven size increase doesn't apply only 
to sauropods. Why would it? I'll point out again that probability is additive. 
 resource utilization/locomotive benefits of size don't mean that "predators 
don't count".
Where's the beef? 


----- Original Message ----
From: Andreas Johansson <andreasj@gmail.com>
To: don ohmes <d_ohmes@yahoo.com>; dinosaur@usc.edu
Sent: Monday, June 18, 2007 3:04:01 AM
Subject: Re: Fw: 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: Sunday, June 17, 2007 5:06:34 PM
> Subject: Re: Fw: late night thoughts: misunderstand what?
> On 6/17/07, don ohmes <d_ohmes@yahoo.com> wrote:
> > ........... I think it unlikely that the first seriously big theropod 
> > appeared before or after the first seriously big sauropod (within the 
> > margin of error). They probably moved pretty much in lock-step. From the 
> > functional perspective, top herbivore/top predator form a predation pair. 
> > The fact that the most extreme cases of giantism in both occurred 
> > simultaneously in geological time is, in my view, evidence for an arms race
> Simultaneous occurence means nothing if you've got non-overlapping
> ranges. *Tyrannosaurus* and *Puertasaurus* are both Maastrichtian and
> of near extremal size for thero's and sauro's respectively, but found
> on different continents. The sauropods actually known from tyrannosaur
> turf are, AFAIK, all comparative runts.
> ............. It seems to me that late in the game, finding the respective 
> maximals well-separated might be viewed as support for a theropod/sauropods 
> size race that began 'at the beginning'.

Which beginning? Tyrannosaurs achieved gigantism independently from
allosaurs, for a start. Where there any really large sauro's around
when the tyrants grew big? Did those mega-sauro's grew bigger in
lock-step until some point where the tyrants won?

Your idea need to be anchored in actual spatiotemporal distributions of fossils.

Andreas Johansson

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