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Re: More on Argentavis



--- Tim Williams <twilliams_alpha@hotmail.com>
schrieb:

> Evelyn Sobielski wrote:
> 
> >Problem is that basically each dataset provides a
> >different tree. Even different sequence-based trees
> >don'tr eally agree well. Also, fossil evidence
> beats
> >inference from any kind of data hands-down. It's
> rare
> >that a fossil say "ain't so", but if it does,
> that's
> >that.
> 
> Ah, but that's not really fair, is it?  ;-) 

OK, so to make it clear: I wasn't talking about this
specific problem. Rather, I referred to fossils in
general refuting branching or timing hypotheses.

Consider the _Icadyptes_ paper, preprint version:
their tree is nice indeed as regards branching
pattern. Their clock is bound to be off, if
_Spheniscus muizoni_ (c.12 mya) *is* a _Spheniscus_
(they find the early SAm taxa to be quite distinct, so
that's arguable). In the hypothesis presented here, at
12 mya only the lineages leading to the basal
spheniscines/phylo-taxo Spheniscidae _Aptenodytes_ and
possibly _Pygoscelis_ had diverged; the date of _S.
muizoni_ is incompatible with the molecular clock.

Even if the SAm _Spheniscus_ are split out of that
genus, the clock is still incompatible with the fossil
record.

Of cource, _S. muizoni_ was not known when the new
paper was written (unfortunately). Maybe it'll be
added in the print version.

"Absence of evidence" of course must be evaluated: are
there sites that might hold evidence but don't, all
things considered? Are there sites that might hold
evidence and have not been worked? "All things
considered" of course requires a robust branching
hypothesis, so that one can consider biogeography. It
requires a reasonable hypodigm so that one can
consider ecology (not much use looking for flightless
landbird fossils in a marine konservat site). For
ratites, we just don't have either.


Eike


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