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Re: Therizinosauroid apomorphies



Honored Person Nick Longrich wrote:

<<-dorsoventrally expanded, laterally directed
anterior iliac blade (nanshiungosaurus, segnosaurus)>>

and Honored Person Mickey Mortimer wrote:

<absent in Beipiaosaurus>

  Hmm, mentioned this before, but Xu (pers. comm.)
says that it is much deeper than illustrated in the
paper, and corrected reconstruction, as well as
demonstrating a well arched ilium, similar to
caenagnathid, therizinosaurid, and "Rinchenia" ilia.
[refs are Currie, 1990, in _Dinosauria_; Barsbold,
1983, in _Trudy_; and Barsbold, Maryañska, and
Osmólska, 1990, in _Dinosauria_.]

<<-edentulous dentary tip (Erlikosaurus,
Segnosaurus)>>

<absent in Alxasaurus (I'm unsure of the condition in
Beipiaosaurus)>

  Russell and Dong (1993) state that the dentary is
incomplete mesiodistally, and may preserved dentition
to the tip; the dentary of *Beipiaosaurus* does also
appear to preserve more mesial dentition, so the
endentulous tip is probably a synapomorphy of the node
== { Segno + Erliko }, which presently corresponds to
Therizinosauridae.

<<-prominent rugosity just dorsal to the posterior tip
of the iliac blade (Segnosaurus, Alxasaurus)>>
 
<not evident in Beipiaosaurus>

  No, so this would appear to be a synapomorphy for
Therizinosauroidea; as it is, Therizinosauroidea == {
Alxa + Erliko }, based on Russell and Dong's
description and diagnosis. The name can be restricted
easily, and Segnosauria can be used for all other
therizinosaurs: == { Erlikosaurus > Oviraptor,
Saurornithoides, Gallimimus, Tyrannosaurus, etc.... }
(or just the first exclusive taxon :).

  Meaning, taxonomically, "therizinosauroid" should be
used exclusively for Alxa, Segno, Theriz, Nanshiung,
Enigmo, and Erliko. "Therizinosaurid" should be used
exclusive _of_ Alxa, and "therizinosaur" or
"segnosaur" can be used colloquially for the whole
group. Just a chip I need to brush off.

<<So even if the apomorphy list isn't overwhelming by
itself due to its spottiness, the rest of the anatomy
is shoving them into Maniraptora and in particular
towards Oviraptorosauria>>

  One odd thing about therizinosaurs is that the arms
are incredibly long. Using Xu et al., 1999, and
running this by Xu Xing himself, the arms of
*Beipiaosaurus* are almost equal the length of the
legs, but doubt must be placed on my statement due to
the lack of a complete humerus. I did, however, use
the combined lengths of the left and right incomplete
humeri (one a proximal, the other a distal half) and
overlapped until the margins didn't correspond, to
reach my humeral length for the reconstruction
(explained this to him), and the arms still came out
very long. Now, attach this to *Therizinosaurus*, and
the typical shortleggedness of very large animals, and
you have a good synapomorphy of ? == { Beipiao +
Erliko }. The arms of "oviraptorine" [excluding
*Ingenia*] oviraptorosaurs and dromaeosaurs are also
very long relative to the hind limbs, though not to
the degree I see in therizinosaurs.

------

  On another claw, Honored Person Jack Conrad
suggested narrowed claws in ornithomimes and
therizinosaurs could be used as a character linking
the two; but, as Honored Person George Olshevsky
pointed out, ornithomime claws are nore neccessarily
narrow. They are generally triangular in cross
section, flattened flexorally, to varying degrees in
the taxa.

  *Ornithomimus edmontonensis* does appear to have
very narrow claws, even in dorsal aspect, but this is
one specimen among ... well ... lots of different
taxa. Most persistent, though, is the prescence of
very flat, spade-like claws in basal taxa, such as
*Pelecanimimus*, and the similar form *Anserimimus*.
Huge, midly trenchant claws in *Gallimimus* and
*Deinocheirus* are the exception, and various
phylogenies place the former near to the
Ornitho/Dromecio/Struthio-complex of Canadian genera.
*Deinocheirus* doesn't seem to go anywhere in my
studies, and little has been made on it. As someone
pointed out before, there is much more than arms and
shoulders in the type, and these need to be
acknowledged (ribs, two cervical vertebrae, gastralia,
and paired ceratohyals [the long, rod-like parts of
the hyoid complex]). Thus, narrow claws are the
exception in ornithomimes, not the rule, and cannot be
used diagnostically except in defining the one taxon
*O. edmontonensis.*

  Additionally, *Segnosaurus* is known by rather --
robust -- claws; they aren't particularly narrowed,
compared to *Therizinosaurus*.

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

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

Qilong---is temporarily out of service.
Check back soon.

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