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RE: Why Thulborn's ideas on dinosaur polyphyly are wrong



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

> Mickey Mortimer wrote:
> 
> >Based on the above, Thulborn finds the chance of
> sauropods and 
> >ornithischians being secondarily > quadrupedal to
> be implausible, due to 
> >the number of changes that would have to occur

But what does "implausible" mean? Certainly not
"impossible". What does the *data* say? "Possible yes,
likely no" is not sufficient as an answer. Are there
conditions under which the morphological elements
needed have an increased chance of evolving in the
right direction? Like all the things that make a
"bird" did in theropods, until the necessary
preconditions were fulfilled and evolution just went
on and took off from there?

You want to know what I find "implausible"? The
molecular scenario that postulated a Psittaciformes
break-up >80 mya, with the Kakapo/nestorine lineage
diverging before the K-Pg extinction. Of course, the
authors summed up the entire fossil record with "many
fossil Psittaciformes have been dated to the Eocene
and Miocene of Europe and the Miocene of North
America, although the precise phylogenetic affinities
of these fossils to modern Psittaciformes have not
been
solved" plus a number of the more recent Mayr et al
papers - but somehow I get the feeling that they don't
have actually read them.

What a pity.

But the difference between the raw data indicationg
that a scenario is *not likely* - though it might
occur in certain cases which may have defined
parameters surrounding them that can be elucidated -,
and one in which the interpretation of two data sets
is actually conflicting to the point that one
interpretation is virtually precluded by the
uninterpreted data of the other set alone.


Regards,

Eike


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