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Re: Late night thoughts: Pathetica and Irony
1). Your "hypothesis" is, you state, that for predator driven size
(size race) to be shown within a given population, minimum size must
increase as well
as maximum size. That is absolutely incorrect within groups composed of
one species. Barring sample bias or data error, if minimum size and
_both_ increase, it is symptomatic of a selective regime in place that is
animals within the group, such as an environmental factor or an illusory
Cope's Rule. Relative to minimum size, it is the exact opposite pattern
a predator-driven size trend in a multiple species population.
Not at all: if all species of such a group are potential prey -- this is
what defines the group --, and if all of them can only escape by growing,
then all will grow or die out.
See here http://www.dinosauria.com/jdp/evol/evolfact.htm for the meaning of
words like "hypothesis" and "theory".
When predator pressure occurs on a multi-species group of the size
(species-wise) and time-frames considered here, some elements inevitably
refugia from the pressure, whether the refugia is environmental,
geographical, or biological.
Adaptation to refugia frequently involves size change, including size
Size decrease is not what you or I would recommend to a sauropod as an
adaptation to predation pressure! Except maybe if it's armored, but only
lithostrotians are armored.
Your statements are tantamount to insisting that in order for predation to
affect size, predation and ONLY predation can be operating, and the
pressure must affect all the potential prey organisms equally across the
This is simplistic, and ignores the fact that probability, and therefore
selective vectors, are additive.
Again: are you saying your hypothesis is not testable? I hope you're not
2). Hone's study, that you so flippantly cite, was testing Cope's Rule. OF
COURSE MINIMUM SIZES HAD TO INCREASE FOR A POSITIVE RESULT.
Perhaps Hone will weigh in on whether he thinks predator pressure had
anything to do
with the size of the mega-sauropods... or whether sauropod size affected
the size of
any of the maximal meat-eating theropods.
Reality check again: not only does the minimum size not increase in
sauropods, neither does the average size, and neither does the maximum size.
You predict an increase of at the very least the maximum size of sauropods
and theropods; the biggest LK sauropods are about the same size as the
biggest EK sauropods, the biggest LJ sauropods except the much larger
*Amphicoelias fragillimus*, and the biggest MJ sauropods (judging from
tracks); the biggest LK tberopods are about the same size as the biggest EK
theropods and the biggest LJ theropods; your prediction is falsified.
3). Patterns found by Carrano evidently support the thesis
of predator pressure and perhaps even a 'predators won'
picture (I hasten to add I do not know of him advancing
that idea or expressing any opinion on it). To paraphrase,
the big sauropods 'sputtered out at the end', and size
decrease in sauropods 'signaled the end of the lineage'. Note
the post-Mid-Jurassic giants that just disappeared. A 'scientific'
skeptic may argue the neutrality of the evidence, the fossil record
clearly does not falsify the concept of predator-driven size selection
Sure it does, according to my results and those of Hone et al.. Carrano
(2005) even found a _decrease_ of sauropod size, which is the _opposite_ of
what you predict (though this may be because he used several immature
4). I thought you would retract, but evidently you stand by this
DM -- "And then there's, again, the fact that neither minimum nor
maximum nor average sauropod (or even sauropodomorph) size increased
across the Mesozoic. Your hypothesis says they did grow bigger, the
fossil record says they didn't, your hypothesis loses. Am I missing
What you are missing with me at this point is credibility.
No wonder. My M. Sc. thesis isn't published yet, so I can't prove that I
really get the results I claim to get. I fear you'll just have to trust me
on that for something like a year.
Except for a bit of sauropodomorph data. In his redescription of
*Anchisaurus* as a sauropod Yates (2004) found a size increase in a sample
of femoral lengths of early sauropodomorphs; I am currently (as the 2nd
author) working on a paper that takes the same sample and the same
phylogeny, adds branch lengths, and finds that there was no size increase.
(Yates used MacClade, which cannot help assuming that all branches have the
same length; we use Mesquite http://mesquiteproject.org, which can deal with
branch lengths; Mesquite didn't exist yet when Yates worked on his paper.)
But of course the sample is incomplete and the phylogeny is outdated
(according to Yates's own more recent results). We'll probably submit this
paper soon, so it should be out in maybe half a year.
Do you want me to spell out the references, or have you got all the papers I
First, it is not my hypothesis; this is the first time I have heard
anyone with any knowledge of evolutionary theory dismiss the
idea that the mega-sauropods weren't driven at least to some
degree by predation.
Yes, but till 2 or 3 years ago it was not possible to test this hypothesis.
Most notably, Mesquite didn't exist yet. And no, you are the first who gives
such prominence to predation pressure as to postulate an arms race; earlier
versions typically assume the sauropods won very quickly and were, when
adult, too big to be attacked by anything.
'Predators won' has also been advanced many times, I would bet.
Never, because that would mean sauropod extinction.
It has been, in fact, consensus that they "got so big to avoid predation,
so they could be invulnerable" for over a 100 years, right?
"Consensus" is exaggerated, but yes, the idea used to be widespread, and no,
it was never tested or even testable until recently, and no, it was assumed
that the sauropods _won_ and that adult sauropods actually _were_
invulnerable, and no, the data completely disagree with any of these ideas.
When the data contradict even a century-long consensus (which we don't have
here), the consensus loses. That's called science. It sometimes gives
MY HYPOTHESIS IS THAT THERE ARE HUNTING STRATEGIES AVAILABLE TO TALL
BIPEDS WITH LARGE JAWS, AND VULNERABILITIES INHERENT TO LONG SKINNY NECKS,
THAT ALLOW ONE TO SPECULATE, AMONG _OTHER THINGS_, THAT 'PREDATORS WON'.
I have tried to show you what predictions _inevitably_ follow from your
hypothesis, and that all of them are falsified. You get emotional and start
Second, the statement that maximum sauropod size didn't increase "across
the Mesozoic" is so bizarre I strongly suspect you are pranking me.
When I make a joke, it's like: "Why do elephants have red eyes?" -- "So they
can hide in the cherry tree."
No, my friend. Show me that *Puertasaurus* was bigger than
*Argentinosaurus* -- hint: _nobody has ever claimed that this was the case_.
We don't even need to take the Late Jurassic *Amphicoelias fragillimus* into
account. Where are you getting your basic assumptions from!?!
And then let's wait for the SVP meeting of 2008 when new material of
*Amphicoelias fragillimus* will be introduced.
Sum-- If you think there are Triassic giants out there, go find one.
That's not even what I said: I said that there is a wide size range in the
Triassic, and that this range increases at both ends in the Early Jurassic,
and then more or less stays the same from the Middle Jurassic through the
Late Cretaceous. An analysis that takes the phylogeny, and not just the
stratigraphy, into account shows that there was no size increase in
sauropods across the Mesozoic. Period.
As to average size, it is not relevant above the level of species, due to
the confounding effects of refugia. Not to mention being so subject to
sample and measurement error as to be laughable. Minimum size has
meaning, _perhaps_, but not the one you ascribe to it.
Confront a small sauropod (say *Amargasaurus*) with a very big theropod (say
*Giganotosaurus*). Assume (as you do) that the theropod can, with a very
high success rate, kill the sauropod by sneaking up and biting it in the
neck. What is the logical outcome?
Confront a middle-sized sauropod (say *Camarasaurus*) with a very big
theropod (say *Saurophaganax*). Same assumptions. Now take into account that
*A.* has these scary neck spines, but *C.* doesn't. What is the logical
outcome? Not the fact that *C.* is the most common fossil in the Morrison
Logical conclusion: something must be wrong with the assumptions.
You said "let's end this one here". That is fine with me. I want to spend
my time on things relevant to hunting strategies, and important stuff like
how long could a sauropod hold it's breath, and I much prefer chess to
tennis anyway.. If you reply to this post, DO NOT DELETE ANYTHING.
And don't intersperse, please. Clear a space above or below, and leave my
words intact so people HAVE to know what I said, and I don't have to say
it again. Thank you! -- Don
- Your e-mail has been sent to the list, so everyone who wants to can read
your words in the original; those people are interested know full well what
you have said. Whether they've understood it is another matter, but not one
I could influence!
- I have of course interspersed. This makes sure I don't overlook any of
your arguments, and it makes sure that people can read your arguments and my
responses together. I don't understand how you can get so worked up by this.
- I always leave an empty line between your writing and mine, in case you
haven't noticed! I also make sure that each quote in each e-mail of mine is
preceded by a ">" when the program doesn't do that automatically. I'm sure
you've noticed that, too.