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

Re: Carniadactylus paper and pterosaur ontogeny



> This is just nonsense. Isometric growth has been demonstrated for
> the forelimb-hindlimb ratio -- and that's it. Skulls most obviously
> didn't grow isometrically in pterosaurs; neither do they anywhere
> else.
>
 You're standing by an unproven paradigm. Show me one juvenile and one
 associated adult to prove your statement.

Science cannot prove, only disprove.

Besides, why would taphonomic association be oh so compelling evidence for conspecificity? And aren't you the one here who's offering an extraordinary claim and therefore has to put some evidence on the table? Parsimony is against you so far.

>> All prior assumptions were just that, assumptions. That includes
>> tooth count, orbit/rostrum ratios, tiny pedal phalanx
>> ossification, scapulocoracoid fusion, sacral fusion, etc.
>>
> Evidence?
>
 Every embryo now known, plus the baby Pteranodon (see below).

(Already treated by Mike Habib.)

>> Put them all into a cladogram and your eyes will pop.
> Phylogenetics obeys the law of "garbage in, garbage out". If I put
> actively misleading scores into a matrix, PAUP* will actively
> mislead me.
>
> Hey, try it. Put either a baby *Apateon gracilis* or a
> postmetamorphic *Apateon gracilis* into a data matrix that contains
> other temnospondyls and lissamphibians, and your eyes will pop.
>
 Don't try to confuse the issue with other taxa. tsk. tsk. Pterosaurs
 follow isometry.

That remains to be demonstrated... against the evidence others have mentioned.

>> Maisano 2004 in JVP provides modern analogs.
>>
> Would surprise me. Could you give me the full reference? No Maisano
> published in JVP in 2004 (SVP meeting abstract volume included).
>
 Sorry, typo. Maisano JA. 2002. Terminal fusions of skeletal elements
 as indicators of maturity in squamates. J Vert Paleo 22:268–275.

Oh yeah, that one. Thanks for the ref.

You know, it really disappoints me that you bring it up again. Last time you did (years ago), several people pointed out that it goes _against_ you: by showing that several bone fusions so far thought to indicate maturity in squamates can actually occur considerably earlier, it shows that individuals can look _more_ adult than they are. It neither says that individuals can look _less_ adult than they are, nor does it mention proportions at all, it's only about, as the title says, "terminal fusions".

>> All the above is proven by adding embryo and hatchling
>> Pterodaustro to any cladogram that has Pterodaustro adults.
>> You'll find they nest as sisters.
>>
> That merely shows that *P.* has a large number of
> ontogeny-independent autapomorphies that are present in these
> matrices. It might be enough to put *P.* (adults and babies
> together) in some wrong place in the tree.
>
 Your guessing wrong. The hatchling and embryos of Pterodaustro don't
 even have skull characters we can use.

Who said all autapomorphies of *P.* have to lie in the skull?

>> Although, it is of considerable interest that the one good
>> complete skeleton of Pterodaustro (adult) has distinct pedal
>> phalanx and metatarsal proportions from the Pterodaustro
>> hatchling. Maybe NOT conspecific.
>>
> These are the very characters that I'd expect to vary with
> ontogeny. Or at least with absolute body size -- there's little
> that still works if you scale it up or down precisely.
>
 The distinct patterns are not as you assume.

Why do you think so?

>> A privately-owned Pteranodon, 1/4 the size of P. marshi (skull)
>> and P.ingens (post-crania) has the proportions of an adult
>> including a fused extensor tendon process.
> So it doesn't have the same relative skull size as either adult *P.
> marshi* or adult *P. ingens*? Did I understand that right?
>
 It has a long rostrum and tiny orbits, like the adults.

_Just_ like the adults? Could you quantify that?

>> Same goes for Bennett's "juvenile" Anurognathus. Unpublishable
>> because it is privately held but a pdf is available through me.
>
> I'm interested in that one.

 Coming by separate post.


Thanks, I got it and have now read it. Unfortunately I can't test any of your bone identifications and reconstructions, because the photos are just abominable. I can say, however, that if your reconstruction is right, this tiny specimen has the relatively _smallest_ eyes of any anurognathid. Either it was much more diurnal than the others, or the reconstruction is wrong (...as the S-shaped reconstructed lacrimal already suggests, frankly). After all, all else being equal, relative eye size doesn't directly depend on ontogeny -- it depends on absolute body size.

BTW, in the manuscript you talk about "the basipterygoid" as if it were a bone. That's confusing. Is that a misunderstanding on my part?

>> The only pterosaurs we KNOW that are NOT adults are those inside
>> eggshells. All other suspects need to be placed into a
>> phylogenetic context to test their nesting.
>>
> What I've been trying to get into your head for the last 5 years is
> that this does not work. PAUP* starts from the _assumption_ that
> all OTUs are in the same ontogenetic stage. If you violate that
> assumption, you introduce mistakes.
>
 Stop. Look at the embryos. They are identical to adults and sister
 taxa adults in all proportions. With isometric growth you CAN use
 embryos in pterosaur analysis.

The last sentence does logically follow from the second-to-last... which, in turn, is unfortunately wrong.

> An important conclusion of my recent work (with Michel Laurin:
> 2008, Contributions to Zoology; 2009, Evolutionary Biology, online
> only so far), already found by other people earlier to some extent
> (check out fig. 10 of Warren 2007, JVP 27(4)!!!) is that not only
> do mistakes in the matrix lead to mistakes in the trees, but they
> lead to mistakes _of unpredictable kinds and magnitudes_ in the
> trees. You can't, for example, say "if there are any mistakes left
> in my matrix, they're tiny, insignificant ones that can only lead
> to tiny, insignificant mistakes in the results" -- _that's not how
> it works_.

 You're going off subject.

Not at all.

> (Naturally I can send pdfs.)
>
 Send them.

Coming soon.

> On the influence of ontogeny, see our 2008 paper: we took a matrix
> that found the lissamphibians as temnospondyls, changed _three
> cells_ from known to unknown because we changed our interpretation
> of the little temnospondyl *Doleserpeton* from adult to immature or
> paedomorphic, and <poof> the lissamphibians came out as
> lepospondyls.
>
 And various fish and insects change remarkably with ontogeny. But
 pterosaurs don't. You must understand this by testing it on
 pterosaurs, not pre-amniotes.

Tetrapods in general, even vertebrates in general, even in fact animals in general have a lot of patterns of development in common. You are saying that pterosaurs are utterly radically different -- you put the evidence on the table, not me.

> Long ago (probably in 2005) I sent you the "ontogeny
> discombobulates phylogeny" paper (Wiens, Bonett & Chippindale,
> Systematic Biology, 2005). Did you ever read it?
>
 Yes. Not pertinent to isometric growth.

If isometric growth in fact existed, which it doesn't.

>> BTW, Bennett from 1991 on notes the bone texture issue appears on
>> immature and mature Pteranodon specimens of the same size.
>>
> Didn't he conclude neornithean-like determinate growth in
> *Pteranodon*?
>
 Yes.

Doesn't that make it irrelevant to more slowly growing animals, in which bone remodeling had plenty of time to keep up with growth?

> (I don't have the paper handy right now.) That's how it looks like
> to me: in many birds, sexual maturity comes after growth ceases, so
> you'd expect immature bone texture in some individuals the size of
> adults because they've just finished growing and are only starting
> to remodel their bones.
>
 I have no problem with that. By my statement I wanted to note that no
 matter the size, immature bone texture may appear, even on full size
 pterosaurs no matter their overall size.

By my statement I wanted to note that you need to look at the reasons for _why_ immature bone texture can appear on adult-sized *Pteranodon* -- because that quickly demonstrates that your generalization about all pterosaurs is invalid.

We're in science here. We're not content with discovering laws, we want to come up with theories to explain them.