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Re: Therizinosauroid apomorphies [long!]



Nick Longrich wrote:

<Some possible synapomorphies:
 
  -obturator process contacting or fused to pubis
(enigmosaurus, segnosaurus, probably
Nanshiungosaurus)>

  The obturator process is displaced to the very
distal end of the ischium in *Nanshiungosaurus
brevispinus*, which is an autapomorphy of the genus
and possibly species (I've yet to see the papers for
both species of Nan, so....).

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

  And most herbivorous mammals. :) *Beipiaosaurus*
also has this condition, though to a less derived
degree, according to Xu (pers. comm.).

  <-first metatarsal with a proximal concavity where
it articulates with the second metatarsal
(Erlikosaurus, Segnosaurus)>

  And *Therizinosaurus.*

  <-spatulate teeth (Erlikosaurus, Segnosaurus,
Alxasaurus)>

  These teeth are not spatulate, but phyllodont
(leaf-shaped) and rhomboid in cross-section, without a
primary ridge, as in the Lufeng jaw in Zhao and Xu
(1998).

  <-very strong lateral compression of pedal unguals
(approached in caenagnathidae)>

  Not neccessarily in caenagnathids; these are
actually broader than in oviraptorids, and exhibit
strongly developed lateral "spurs" ont he ventral
surface, similar to ornithomimosaurs.

  <-manual ungual II longer than ph II-2 or MC II
(Therizinosaurus, Beipiaosaurus, ?Alxasaurus)>

  And in *Ingenia*!

  <-extreme expansion of distal humerus (Erlikosaurus,
Therizinosaurus)>

  Quantify.

  <-short, robust manual phalanges and metacarpals
(Alxasaurus, Therizinosaurus)>

  And *Beipiaosaurus*, of all things. The metatarsal
III is only one fourth the length of the tibia.

  In addition, a sharp, prominent tubercle is present
on the posteromedial edge of the humeral shaft in
*Therizinosaurus*, *Erlikosaurus*, and *Beipiaosaurus*
(Maryañska, 1997, and Xu et al., 1999). The pubic
peduncle of the ilium is 2x or more the length (or
depth) of the ischiadic peduncle. As Mickey Mortimer
notes, the astragalar ascending process is turned
lateral to the lateral margin of the tibial shaft, in
*Segnosaurus*, *Therizinosaurus* and *Beipiaosaurus*;
and it covers the fibula in flexor aspect in
*Segnosaurus* and *Therizinosaurus.*

<I seem to recall that there is a partial skull for
Segnosaurus, showing the same inflated basisphenoid of
Erlikosaurus.>

  Not for *Segnosaurus*, but *Beipiaosaurus exhibits
the partial cranium and maxillary fragment, and
*Segnosaurus* does have a lower jaw.
  
<The skull of Erlikosaurus shows quite a few
oviraptorosaurian features (medially short nasals...>

  Pardon?

<...ectopterygoids lateral to palatines),>

  And separate from the maxilla or jugal laterally, so
that the lateral palatal vacuity is confluent with the
lower adductor vacuity. (Also present in
Oviraptoridae, so may be a synapomorphy of *Oviraptor*
+ *Erlikosaurus*.)

<Russell has argued that therizinosaurs lack a
supracetabular crest,>

  *Beipiaosaurus* has one.

<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- largely confined to the same
branch of the tree, they pretty much have nowhere to
go except with each other. At least that is how I
interpret it.>

  I list the following synapomorphies for ovis +
therizinos:

  1-edentulous premaxillae [teeth in *Caudipteryx*]
  2-basipterygoid processes reduced
  3-medially inflected dentary [also in troodontids]
  4-lateral depression in the middle-ear cavity [same]
  5-no maxillary fenestra [present in oviraptorids?]
  6-caudals reduced to 35 or less
  7-caudals consistently reduced in length
  8-posterodorsal lip on first manal ungual, sometimes
on other unguals
  9-preacetabular blade deeper/longer than
postacetabular blade [the first is reversed in
*Inegnia*, present in *Achillobator*]
  10-ectopterygoid separate from maxillae or jugals
  11-propubic boot longer than postpubic boot

  Six of these may be autapomorphic, which I think is
substantial enough. If someone could run them in Paup
or MacClade... [Do you DELTRAN or ACCTRAN, Mickey?]

  Six sacrals are known in *Velociraptor* (Norell and
Makovicky, 1997), *Gallimimus* (Osmolska et al.,
1972), and troodontids (Barsbold, 1976; Currie, 1990;
Paul, 1988). Cervical and presacral pneumatization is
variable, and *Microvenator* lacks pleurocoels,
*Achillobator* has cervical, dorsal, and caudal
pleurocoels (Perle et al., 1999); Caenagnathidae and
Therizinosauroidea may have aquired their pairs
separately because *Caudpteryx,* *Avimimus* and
*Microvenator* lack the condition -- this is of course
assuming they are within Ovi + Theriz.

   Somebody got the two *Nanshiungosaurus* papers on
hand so I can get photocopies? Translations, too?
Nessov, 1995, would also be nice... :)

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