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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!