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Re: Therizinosauroids (was Re: Giant Birds)



Jaime Headden wrote-


>14 characters exclude *Caenagnathasia* from Oviraptoroidea, on the basis of
shared postcranial and cranial characters of
Caenagnathidae and Oviraptoridae.

How could shared postcranial characters exclude a taxon known only from
cranial fragments?  Or has more been discovered of Caenagnathasia besides
the original dentaries?

>both Caudi and theriz's have a
>notch in the pubic pedicle, suggesting the
>disarticulated pubis in Caudi was retroverted.

I know Caudipteryx has this and Segnosaurus would appear to also, but it
would seem to be absent in Beipiaosaurus, Alxasaurus, Nanshiungosaurus and
Enigmosaurus.

>All have a fairly short ischium, a feature I see a _lot_
>in "mesopubic" maniraptorans/maniraptoriforms
>including "dinobirds" such as *Rahonavis* and
>*Unenlagia* (even *Sinornithosaurus* has the requisite
>features of a mesopube even though the pubic pedicle
>is deeper than the ischiadic one);

Ingenia (the only oviraptorid for which I have this information) has a
plesiomorphically elongate ischium, as do all therizinosauroids that can be
measured (Alxa, Segno, Enigmo, Nanshiungo).  Caudipteryxs' is just barely
shorter than the plesiomorphic condition (as seen in compsognathids,
Scipionyx, tyrannosauroids, Ornitholestes and ornithomimids).

>a good name for the ovi + dromie + theriz group could therefore be
>"Mesopubes". There are numerous other features grouping them.


This equals "Maniraptora" in my and others' analyses.

>Ovis, dromies, and theriz's have locked scapulocoracoids,
>caenas don't;

What do you mean by this?  I thought that only Rahonavis, among
non-pygostylians, had a mobile scapulocoracoideal joint.  Or perhaps you're
speaking of something else.

>  There's a lot of convergence in these groups that
>really might be resolved soon by Clark et al.


I certainly agree with that.

>  Feed ornithomimosaurs into the comparisons, and we
>get a whole lot of more fun. While much of the dromies
>+ oviraptorosaur characters may be autapomoprhic, many
>of these features I listed above are shared almost
>universally in ornithomimosaurs, including theriz's,
>which argues a lot for plesiomorphy of much of this in
>maniraptoriforms, so that ornithoms, theriz's, and
>ovis form a group exclusive of the maniraptorans troos
>and dromies et al. Much of this agrees with what Peter
>Buchholz (onlist and off) and Paul Sereno (presswise)
>have talked about.


Well, the arched ilium with high preacetabular process is developed in
Harpymimus, though other ornithomimids seem to be more plesiomorphic in this
regard.  Ornithomimids certainly haven't shortened their ischium.  In all of
my analyses, ornithomimids fall out basal to oviraptorosaurs, Caudipteryx,
therizinosauroids, dromaeosaurs, troodonts, Avimimids, alvarezsaurids and
birds.
I used to also believe in a ovi-theriz-ornithom group, but most of the
synapomorphies fell out as plesiomorphies later reversed or convergences in
the most parsimonious trees.

Mickey Mortimer