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Re: Ah ha! That's where therizinosaurs came from
On 15.08.2011 05:12, Mickey Mortimer wrote:
Gregory Paul wrote-
> The potential link between jeholornids and therizinosaurs is much
> weaker than that between omnivoropterygids and oviraptorosaurs. The
> reason that jeholornids are interesting is because they show that
> long tailed herbivorous fliers were out and about, and were
> potential ancestors for neoflightless long tailed herbivores like
> basal therizinosaurs. Jeholornids make poor ancestors for
> therizinosaurs in part because they lacked tooth rows (which are
> unlikey to have reevolved although it cannot be ruled out).
If you actually suggest some synapomorphies, I could include them in
the upcoming paravian analysis and see if they have an effect.
I'm looking forward to that.
I wasn't the one who made the argument, but the problem with your
reasoning is that while your neoflightless idea seems to be at least
partially right, as were several of your other ideas, your
precladistic phylogeny also got a lot wrong (assuming for the moment
the current consensus is right). [...] Cladists were making some of
the same mistakes, but Gauthier (1984, 1986) got the correct position
for ornithomimosaurs and oviraptorosaurs for instance. So if you
would have been a cladist, you might have gotten priority for other
ideas even if your analyses didn't find basal maniraptorans to be
bird-like. It's not fair to point to what your intuition got right
as an argument against cladistics without also taking into account
what it got wrong. The difference is that whether a cladogram's
right or wrong, we can objectively examine the support for any
topology and see which characters and taxa were taken into account.
But even if your intuition is right, we can't do anything with it.
Matthew and Brown's (1922) intuition was right that tyrannosaurids
were coelurosaurs, but since the character evidence they provided
doesn't actually support that conclusion (elongate quadrate well
attached to quadratojugal, short peduncle on ilium, arctometatarsus),
is it really justified to credit them with getting it right just
because subsequent finds have made it most parsimonious?
In short: it's possible to be right for the wrong reasons, and it's very
important in science to draw conclusions for the right reasons. The
wrong reasons will only lead one to be right at random and in rare
cases, while the right reasons... tend to be... more reliable.
> My therizinosaur paper in JVP in 84 actually was a shot at
> something at cladistic analysis -- and look at where that got me.
> The reason therizinosaurs were such a phylogenetic problem was the
> absence of sufficient fossils. As more data became available they
> proved to be derived theropods after all.
Actually not true. If you scroll down to the "Experiments with
Controversial Taxa" section on
http://home.comcast.net/~eoraptor/Gauthier%201986.htm , you'll see
where I added Segnosauridae (based only on Segnosaurus and
Erlikosaurus) to Gauthier's classic 1986 dinosaur analysis. They
emerged as maniraptorans just as they do today, even though
Ornithischia and Sauropodomorpha were both OTUs. Your 1984 analysis
was hindered by including few theropod characters, and only using
coelophysids and dromaeosaurids as your theropod sample. Of course,
you could argue Gauthier's didn't include the relevent characters
uniting segnosaurs with herbivorous dinosaurs. But since it was a
cladistic analysis, we could actually test that idea, whereas
intuitive analyses can't be dealt with objectively.
That's what I love about science -- the scientific method isn't limited
by our imagination!