Re: Philosophies for Character Ordering

[Mickey Mortimer <Mickey_Mortimer111@msn.com>]

Jaime Headden wrote-

> Now, if these are all ordered, we get one tree.
> (Tyranno(Ornithom(Confuc,Protopt,Sinornis))).
>  The fact Confuciusornis and Protopteryx have an intermediate state
> between Ornithomimus and Sinornis for characters 1-3 DOESN'T make them
> form their own clade to the exclusion of Sinornis.  Just like the fact
> Ornithomimus, Confuciusornis and Protopteryx have an intermediate state
> between Tyrannosaurus and Sinornis doesn't make these three form their own
> clade to the exclusion of Sinornis.  This is how almost everyone codes
> characters.>
>
>   Naw. Not really. *Sinornis* has a condition unique only to itself (as it
> is considered transformed from the state in other birds). As stated by
> myself, other features of these birds should alter this. Change half the
> characters to unordered, and you get a different set of conditions, and
> the phylogeny changes, as some similarities will be shaped related as well
> (as Wilson stated). Suddenly, half these characters become potential
> apomorphies (my point). Ordered, the characters are step-wise and will
> produce this effect. As I've stated before, assumption of ordering assumes
> an unknown transformation sequence (as Wilson has repeated).

Yes.  Yes really.  All other analyses of dinosaurs I've seen besides Wilson
(1999, 2002) treat changes in phalanx and vertebral number as ordered.  It
doesn't matter if other characters would change the experiment's topology,
it's there merely as an example of the effect of ordering characters.  It
seems almost everyone assumes the transformation sequence of vertebral and
phalangeal counts is known, or else they couldn't say Tetanurae was
characterized by having "one OR LESS phalanx on manual digit IV".  We assume
taxa with one phalanx are closer to taxa with no phalanges than either is to
a taxon with two phalanges, if the outgroup has multiple phalanges.

> <Notice how in three of these trees, Confuciusornis and Protopteryx clade
> together to the exclusion of Sinornis because of their intermediate
> state?>
>
>   Yes, the state becomes synapomorphous.

But do you think most paleontologists accept that?  Ask them "Do you think
we can group Coelophysis and Ceratosaurus together to the exclusion of
Ornithomimus and Sinornithosaurus because they have two phalanges on manual
digit IV instead of none?" and I think they'll say "No, that's a
symplesiomorphy Coelophysis and Ceratosaurus share".

> <And how it can't tell Sinornis is closer to Confuciusornis and
> Protopteryx than Ornithomimus is, despite the fact the birds are more
> similar to each other in characters 1-3?  I have a problem with this, and
> I'm sure others do too.>
>
>   This is not a flaw of the theory, but of the lack of robusticity. No one
> will be running an analysis of this brevity in taxa and characters. John
> Pourtless pointed out the 9 taxon, 35 character analysis of Mayr that just
> screams "NOT robust" as being why such consistency among some taxa would
> be easy to support. MORE characters, MORE taxa.

Robusticity isn't an issue, this is just an illustrative example.  Given the
five characters, most people would agree the "ordered" topology is the one
suggested by the data.  But Wilson's arguing the "unordered" topology is
just as well supported.

Mickey Mortimer