re: was ... Jaime. Now: M. Baeker has a problem with phylogenetic analysis

[Martin Baeker <martin.baeker@tu-bs.de>]

> > Just tell me how it would be possible to demonstrate that a juvenile
> > belongs to a parent if they are to look completely different.
> 
> Try to not use the all inclusive phrase: "completely different". Because even
> elephants and flies are symmetrical. If you find it too difficult to come up
> with an adult/juvenile pterosaur pairing, go to the literature and see what
> forms Wellnhofer and Bennett have promoted as adults and parents of the same
> genotype. Then expand the universe of taxa to include all pterosaurs and
> you'll find that rather than matching parents, the so-called 'juveniles'
> actually form series that fill phylogenetic gaps between taxa. It's not an
> isolated incident. Happens about six times.

So, once again, your argument is as follows:

If I assume these small pterosaurs are adults, I get a cladogram I
like, therefore they are adults. 


> In pterosaurs they do, as embryos tell us. Chiappe and Co. told us one embryo
> was Pterodaustro because it was found with and looked like adult Pterodaustro.

Thanks for pointing me to this article, I hadn't looked at it, at
least not recently.  But read the nature article closely:

"The relative sizes of limb elements of the specimen, which give an
estimated wingspan of 27 cm, are similar to those of early juvenile
specimens of Pterodaustro and agree well with allometric observations
based on a growth series of this taxon indicating negative and
positive allometry for the proximal (humerus and ulna) and distal
(metacarpal IV) portions of the wing, respectively."

This translates as: The embryo does *not* look like an adult
pterodaustro wrt limb proportions, but the juveniles known provide us
with enough knowldege of *how the bones grow differently* to ascertain
this as a pterodaustro (and the filter-teeth surely help.)

But if you would now code this pterodaustro as an adult for use in a
cladogram, the differences in the limb proportions would place it not
at the same place as the adults - you would get a nice series from the
embryo through juvenile to the adult.


> > It can't if you plug in units (specimen or species) *that differ in
> > more than just phylogeny*.
> 
> Example please.

You don't really need that, it is obvious from the theory behind the
cladogram. You can plug in *anything* into PAUP if coded correctly and
it will produce a cladogram. Try car brands, languages, whatever. What
you will get is an ordering of the things you plugged in - this
ordering can be assumed to be phylogenetic if and only if phylogeny is
the only thing what the units you plugged differed in.

> Phylogeny is easier than you think.

I'm afraid it's more difficult than *you* think...

Martin.

                   Priv.-Doz. Dr. Martin BÃker
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