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Re: Hanson 2006, Mortimer, Baeker response


On Jun 12, 2006, at 2:44 AM, Martin Baeker wrote:

A metaphor for what you are saying is: "Don't cross the street. You might get
hit by a car." Many referees do the same thing to everyone's frustration.
Without saying so specifically they throw out such general red herrings and
orange cones by saying essentially: "It's possible that what you are doing is
in some unspecified way dangerous." 

No, I think what Mickey said is "The number of MPTs you get in the end
is not a measure of the quality of the analysis". If knowledge of the
fossil record is incomplete, you would expect a large number of MPTs.

Your argument looks like a classical logical fallacy:

"The correct, perfect analysis should have only one MPT.
My analysis produces only one MPT.
Therefore, my analysis is correct."

No Martin, here's the deal:
You wrote: "If knowledge of the fossil record is incomplete."
There are levels of incompleteness. As in dinosaurs, in pterosaurs we've gotten to the point where very few really strange lineages are showing up. Most, if not all, dinos and pteros found today can be placed into existing slots. Examples of new dinos include Lotosaurus and Silesaurus, but these have been slotted into Ornithischia without a retro pubis. Examples of new pteros include Austriadactylus, Bakonydraco and Pterorhynchus, all of which have nothing else exactly like them, but can be slotted into an existing cladogram. If you have a cladogram that includes all known pterosaurs and you have one MPT, plus the cladogram is chronologically correct and there are no untennable reversals, then you've achieved your goal. Note that reversals are still permitted, but untennable ones are not.

So, knowledge of the fossil record is incomplete in one sense, but complete in another. Sorry. Some of the mystery is gone now.

My single MPT is chronologically accurate, avoids untenable reversals, puts
derived characters at the tips of branches and bottom line: you can line up
the taxa in a visual spectral blend like rhipidistians emerging from the
swamps and morphing into humans lurching over computers. 

Shouldn't that make you suspicious? It would be the first cladogram I
ever heard of that contains nothing like ghost lineages, things
disordered wrt time, reversals (shouldn't we *expect* reversals?
Evolution is not directed, after all.) etc.  It would mean that our
knowledge of pterosaurs is complete and perfect.

See above. Our knowledge of pterosaurs is complete and perfect in one sense. Incomplete and imperfect in another. You can see the layout of this particular jigsaw puzzle because the corners and borders are in place. Holes are still present, but they merely complete a picture that is already recognizeable. Using your logic, no one will ever find the cladogram that echoes Nature. You're suspicious of an answer that fulfills all your requirements for a correct answer. I hope you see that. 


It passes any test
you can put upon it.


This is really a dangerous statement to make. Did you think of and try
all possible tests?  As Feynman said: "The easiest person to fool is
yourself."

You sound like a referee. Afraid of the 'danger' of finding a really good cladogram.

Just as I have tested this cladogram in every way possible, this is a challenge to others to let it get published and/or test it yourself. I'm not so much bragging about this cladogram as I am challenging any worker to knock it down with evidence so it can be changed for the better. Can you do it? I'm hoping you can. If there is a mistake here, I want to know about it.


Anyone who claims No. 9 is a baby Pterodactylus and not a minute
variation of Scaphognathus will have to do so scientifically, perhaps with a cladogram. 

How could a cladogram prove such a thing? It can only sort beasts
based on characters, but it cannot find out the meaning of those
characters. To see whether something is adult or not, look at bone
sutures, or, even better, bone microstructure (see the Europasaurus
paper for an example of this).

A cladogram, I remind you, is a hypothesis. I promote this particular hypothesis because it works in every way. A hypothesis doesn't prove anything, but it is the best evidence (and usually they are widely accepted) that we have. So, so far it is a good hypothesis based on more evidence and less a priori assumption than any in its category.

But let's take the opposite stance.

Let's say that No. 9 is a juvenile. What is it a juvenile form of? Be specific and show evidence that it is indeed the candidate you propose and that it doesn't have more evidence (remember parsimony) that it is closer to my candidate.

Next point: do pterosaurs change their morphology during ontogenesis? Or not? The embryos in eggs are the only known pterosaurs for which their ontogenetic age is known precisely. Morphologically do they look like adults of one form or another? Or are they unclassifiable? My evidence indicates that embryos look like parents, and I used a cladogram. If embryos look like their parents, I think we should expect that juveniles do too. Don't you?


The smallest known pterosaurs, I remind you, are no smaller, nor in any
parallel universe different than the smallest known adult birds and bats. They
are volant from the time they leave the egg. 

True, but we are not talking mammals or birds here. If you look at the
growth rate of, say, a t rex, you can (with some reasonable assumption
on mortality) easily calculate that the *biomass* of small rexes (less
than 1 ton) was probably larger than that of adult rexes. Meaning,
juveniles filled a different ecological niche, and probably filled it
very well. If the same held for pterosaurs, then there were lots of
tiny pterosaurs filling the small-size ecological niche - just not of
a different species.

Thank you for that. I'm not following your argument though. No one making a cladogram cares what tiny pterosaurs ate versus what big pterosaurs ate. Or where they lived. Or what they did with their spare time.

I also remind you that the smallest adult lizards can fit comfortably on a
dime.

For pterosaur adults, this would mean they would eitehr have to give
up homoiothermy or they would need an incredible amount of food (like
an etruscean screw, for instance). Not impossible, but it's a stretch, I think.

Again, no one making a cladogram cares what temperature pterosaurs were. But you bring up an interesting point. What happens with baby sauropods versus big sauropods? We know what size baby pterosaurs of any adult species were because the egg chute has a limited aperture. We can start from there. Just think how small a baby of a tiny pterosaur would have to be. Lizards are remarkable, aren't they?

David



Martin.

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