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RE: Essentialism and such (was a bunch of previous subject lines)



> This is hardly the only case of people using this
> sort of logic. It would make sense if such "types"
> (NOTE: we are NOT talking
> "holotypes" here!) were real, but instead they
> aren't. There isn't a "theropod" type any more than
> there is a "dinosaur" type or a
> "reptile" type. There is instead descent with
> modification.

To which might be added, "bird type", as we have begun
to see since a few years. Methinks it is still sinking
fully in, but I would consider it to eventually show
the strongest potential as a showcase of evolution.
Chiefly because it initially seems to *defy* logic -
and indeed prolly does, but nonetheless there starts
to emerge a pattern - it is neither random nor
apparently directed. In your face, creationism and ID!

Water-land transition, as it currently stands, could
conceivably used by ID supporters as "proof", because
the fossil record is still bad enough to allow
speculation of "guided" evolution.

Returning to typology, Barsbold's "ornithization" adds
a nice twist to the issue. Initially it seems like
typology, but it can't be farther from that. It's not
a testable scientific hypothesis (more like a
throwaway line) and never was meant to be - but the
idea that theropods happened to find themselves in
possession of a set of incipient "avian" features
which were subsequently developed by various lineages
to varying extent in varying combinations and led to
some sort of feathered flight in some lineages -
indepently, even - is interesting since in 1983, it
was not even well-supported enough to be a prediction
but by now, there is mouting evidence that it is
indeed what may have happened.

This does not even remotely tough avian, let alone
neornithine monophyly, because it is a matter of the
available data to sort *that* out. BUT it is a nice
explanation for the large number of
Early/mid-Cretaceous oddballs, because the underlying
assumption is that any theropod lineage could, in its
own particular manner, "ornithize" at any given time.

"Ornithization" is the best I have yet seen to explain
alvarezsaurids, Nomonia, Microraptor, Rahonavis,
Vorona, Mei, Caudipteryx, Yandangornis etc pp:
different combinations of different modes of
development of incipient "bird" characters which in
some led to flightlessness and in others didn't.

The typological "bird" is a paraphyletic
pseudo-entity. I think we can all agree upon that.

And if we go and thoroughly check for homoplasy in
"avian" characters - as has been done and methinks
sufficiently proven for feathers and toothless beaks -
it actually becomes a testable scientific hypothesis.
I believe that the distinction between cladistics and
phenetics is not as clear-cut as it may seem: any
cladistic approach which has a too broad scope of
characters essentially *becomes* phenetics: Cracraft's
infamous 1982 "Phylogenetic relationships and
monophyly of loons, grebes, and hesperornithiform
birds" was methodologically cladistics, as clean as it
could get at that time - but what he *did* was present
a conclusion that could only be considered phenetics
because his choice of characters was too coarse and
thus he ended up with a cladistic comparison of
overall similarity.

Regards,

Eike


        

        
                
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