Re: Placement of Segnosauria

["Jaime A. Headden" <qilongia@yahoo.com>]

You wrote:
 
<Couldn't that be alvarezsaurid?>

  Could be a lot of things, including basal
ovi+therizino. Extensive fusion of elements, narrow
iliac blades as indicated by the short sacral ribs,
pleurocoels on the first couple sacrals but not on the
more posterior ones.... Though alvarezsaurs have a
concave cranial face to the first sacral, as does this
specimen, so do a lot of maniraptoriformes, usually
indicative of either a platycoelous, amphiplatyan, or
procoelous last dorsal vertebra; or the acoelous last
dorsal of alvarezsaurs. Like I said, this sacrum could
be anything. I usually assume it is Maniraptoriformes
incertae sedis, but I could be wrong; this is the most
parsimonious position in my opinion.

<<Therizinosauroid manal claws from Morocco (Russell,
1995, _Comptes Rendus_) are rather quaint...>>

  More on these later, I think I've mentioned them on
the list once or twice. Or not. Figured but not really
compared to much of anything, they have ovi+theriz
similarities, as well as ornithomimosaur features, the
"Therizinosauroid" term being the adjective of
similarity, not referal. Puts diverse "bird-style"
maniraptoriforms in Africa.

<But in these, the distal carpals 1 + 2 are never
fused, whereas they are in ALL (neo?)theropods...>

  My two cents though this was in reply to Pete
Buchholz (sorry, dude :)):

  Huh? Ornithomimosaurs and tyrannosauroids do seem to
indicate separate distal carpals 1 + 2, as does Kirky,
that funky little *Nqwebosaurus.* Chure, Holtz, and
others have been reevaluating the form of the carpals
in theropods and such, but lack of fusion is hardly a
decisive feature anymore. At least as far as the
presented evidence indicates. Avian-style carpal block
appears in several forms, with the pulley-like
proximal hinge and semi-lunate profile, palmar [volar]
condyle shorter and lower than the extensor [outer]
condyle, so on, is a feature that also persists
throughout Theropoda, Sereno and Novas (1995) and
Sereno (1999) described it for *Herrerasaurus;* Chure
(1999) has recently described it for *Allosaurus*, the
condition in ornithomimosaurs, including
*Deinocheirus* and *Pelecanimimus* is unique as they
are all flattened discoid "thingies," and the
condition of fused, giant block covering the proximal
surfaces of the first and second metacarpals occurs in
only troodontids, dromaeosaurids sensu stricto [_not_
including those newbie and wierdie things like
*Achillobator*, though this region is not preserved],
oviraptorosaurs, birds, etc. Holtz recently ran a list
of changes and some papers to follow up here on the
list earlier this year or last last, sometime around
the 59th SVP [Denver]. The condition of the manus in
*Therizinosaurus,* *Alxasaurus,* and *Beipiaosaurus*
are all very homologous, with short third metacarpals,
really long fingers, giant claws, no twist-thumb
(Bakker and Galton, 1974?), dorsoproximal flexor
"lips" on the claws, identical semi-lunate but unfused
carpal blocks, first metacarpal appressed to second,
and so on, that argue for sympatry at least. In the
hand. There's more, and the biggest case for
*Beipiaosaurus* being a theropodan segnosaur is in the
foot, previously mentioned on this list, thus in the
archives, and the links Pete Buchholz provided will
get you to the other threads, I'm sure.

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