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Re: news from dino central



David Marjanovic wrote-

> This is quite basal indeed. Convinced me :-) But tyrannosaurs don't have
an
> ischial foot...

This is true.  However, other characters apparently override the ischial
foot in my phylogeny.  Note that ornithomimids also have an ischial foot,
but are always above tyrannosaurids.

> > Oh look at that, two synapomorphies.
> > - ulnar shaft bowed
> > - semilunate carpal
>
> How did these come out as synapomorphies? I mean, lots of others have one
or
> both... *Ornitholestes*? Maniraptoriformes? ~:-|
> How do you define the semilunate? Does *Allosaurus* have it, or does it
have
> to be bigger, like in e. g. *Ornitholestes* and dromaeosaurs?

In PAUP you have to realize that synapomorphies are often very homoplasious.
I have my analyses set on DELTRAN, so characters will appear as high up as
possible in a tree.  So if there is a phylogeny like (Tyran ((Coelur,
Scipio) (Ornithom (Ovirap, Dromae)))) and I have both bowed ulna and
semilunate carpal coded as (0 ((1, 1) (0 (1, 1)))), PAUP is going to say it
evolved in parallel in Scipionyx+Coelurus and maniraptorans.
Ornitholestes has a bowed ulnar shaft, but its carpus is unknown.  Some
maniraptoriformes lack bowed ulnae (ornithomimosaurs, segnosaurs,
alvarezsaurids, compsognathids- if they are maniraptoriformes) and some lack
features of a semilunate carpal (unfused- segnosaurs; no trochlea-
ornithomimosaurs).  The complexity of the semilunate carpal was one of the
reasons I decided to refine the character when reading Holtz 2000.  My new
semilunate character is "semilunate carpal expanded to cover metacarpals I
and II", pretty much taken from character 253 of Holtz 2000.  This is a
pretty good maniraptoran synapomorphy.  The semilunate carpal of carnosaurs,
tyrannosaurids, Coelurus, Nqwebasaurus, Scipionyx and ornithomimosaurs is
smaller.

> > Eotyrannus is finally grouping with tyrannosauroids.
>
> Why "finally"? Didn't it before? Is it _so_ basal, or just too
fragmentary?

It's very fragmentary, with some characters (fused interdental plates, last
sacral centrum pleurocoelous, no coracoid foramen, etc.) that like to
override the few tyrannosauroid characters and place it with maniraptorans.

Mickey Mortimer