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Re: Therizinosauroids (was Re: Giant Birds)



Mickey Mortimer wrote:

<Indeed, Caudipteryx does share some synapomorphies
with caenagnathids that oviraptorids lack. These
include a slender third manual digit,>

  All maniraptorans (including troodontids) have a
slender third manual digit; this is especially telling
in dromaeosaurs, oviraptorids, and caenagnathids,
where the digit is slender enough with a bowed mcIII
that it can cross under digit two. In flexure, the
digit opposes d-1, with d-2 neutral in position. It is
parallel to d-2 in extensure, but d-1 reverses and
points away from the rest. This is true in all these
taxa.

<a centrally located ascending process of the
astragalus that does not expand laterally>

  Based on *Chirostenotes* (as the distal end of the
tibia in *Elmisaurus* is not known sufficiently to say
"caenagnathids") the ascending process is convergent
with the lateral edge of the tibia; the problem is,
with the RTMP 79.20.1 specimen (Currie and Russell,
1988) the tibia has been crushed flat so that the
lateral and anterior surfaces of the tibia are exposed
on the same plane, making the asc.proc. appear
centralized. I assure you, it is quite similar to
*Ingenia* (Barsbold et al., 1990) but narrower, and
with a higher fibular crest and narrower distal end.

  *Kakuru*, on the other hand (or leg?), does have a
centralized asc.proc., an autapomorphy of the genus et
species (Molnar and Pledge, 1981).

<and possibly a surangular fused with the articular.>

  Indetirminate in as far as the illustrations,
descriptions, or photos in the paper (Ji et al., 1998)
are concerned. Morphology of the jaw, however, shows
the articular is of a glenoidal form, rather than a
condylar form, as in *Avimimus* (Kurzanov, 1984, 1985;
1987), but not as in oviraptoroids [=
"caenagnathoids"].

<By the way, therizinosaurs and oviraptorosaurs also
have a proximodorsal lip on the manual unguals that
Caudipteryx lacks (Currie pers. comm. 1999).>

  Yes, and some ornithomimosaurians (*Pelecanimimus*
[Perez-Moreno et al., 1993], *Deinocheirus* [Osmolska
et al., 1971]) have them, too. This is one of those
features I was mentioning yesterday (for me, anyway)
as being homoplastic in maniraptoriforms, possibly
lost in some taxa, but retained in others.


=====
Jaime "James" A. Headden

"Come the path that leads us to our fortune."

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