Re: Revising Hou et al, 96 (very very long)

["Mickey Mortimer" <Mickey_Mortimer111@msn.com>]

_Rutger_ Jansma wrote-

> If it is important in this matter, in my soon-to-be finished skeletal
> reconstruction, the pubis in Beipiaosaurus comes out mesopubic. And when I
> first started, my first guess was that it was propubic, but since there is
a
> small fragment of bone (probably a small piece of pubis), attach the
> relatively complete shaft of the pubis to this bone, and voilá, we have a
> mesopubic Beipiaosaurus! This also correlates with the amount of evidence
> known from more advanced genera succeeding Beipiaosaurus, they show a
shift
> from the more mesopubic position (Alxasaurus (condition not precisely
known,
> but very probable IMHO), Beipiaosaurus) to an position approximately in
the
> middle (Nothronychus) to the avian opisthopubic
> Segnosaurus and Enigmosaurus.

I'm not sure if the small fragment adhering to the pubic peduncle is
actually a part of the pubis.  The main pubic piece seems to be in anterior
or posterior view, so does not help the situation.  I also made a skeletal
reconstruction, which shows the pubis being barely propubic.  It seems in
general we agree that segnosaurs were moving from something close to a
mesopubic condition to an opisthopubic one.

> This is something I can be happy about! One mesopubic ancestor in the
middle
> Jurassic (speculation, speculation, speculation...) could have given rise
to
> the two "clans" of Maniraptors: a propubic one (Bagaraatan and in the
> Segnosaurs and Alvarezsaurids this was reversed) and an opisthopubic one
> (Deinonychosaurs, avialans). Wonder how this animal would look like, maybe
> something for a list discussion: create your own basal Maniraptoran!

Well, I agree regarding a split between enigmosaurs (perhaps basally
mesopubic) and eumaniraptorans + troodontids (probably basally opisthopubic)
in the Middle Jurassic.  Bagaraatan probably split off somewhere around here
too, perhaps at the base of one of those clades, or perhaps a bit earlier.
Alvarezsaurids might have been closer to troodontids + eumaniraptorans, or
might have been the first known maniraptorans to diverge.

> The dice could roll
> either way, for now, I'm sticking to Xu et al's 1999 and their diagnosis
> untill something better comes along with the needed evidence to support
> either of the theories or hypothesis.

Well, there's always my 2000-2001 analyses, which included all the
characters Xu et al. did and much more, along with a lot more taxa.  Looking
at the deinonychosaurian characters Xu et al. found in Sinornithosaurus-
1. T-shaped lacrimal.
Very widespread, also being found in ornithomimosaurs, oviraptorosaurs,
Avimimus, troodontids, confuciusornithids and the Spanish nestling
enantiornithine for example.
2. supratemporal fossa extending anteriorly at least to above posterior
margin of orbit
Present in Acrocanthosaurus, Sinraptor and virtually all coelurosaurs.
3. T-shaped quadratojugal
True, though also found in Erlikosaurus.
4. quadratojugal fenestra wide open
True for Velociraptor, but not Dromaeosaurus.
5. dorsal and ventral margins of dentary subparallel
As often as I've seen this character used, the condition in dromaeosaurs
doesn't look any different from other theropods to me.
6. Elongate distal chevrons and prezygopophyses
Also in Microraptor, which is even more bird-like (but still thought to be a
deinonychosaur by many).
Characters shared between Sinornithosaurus and birds, but not
dromaeosaurids- premaxillary body low; unserrated premaxillary teeth;
quadratojugal-squamosal contact absent; smaller angle between scapula and
coracoid; more transversely oriented distal coracoid; more than three pairs
of sternal ribs; boomerang-shaped furcula; metacarpus over 40% of femoral
length; no anterior pubic foot; proximodorsal ischial process; mid-dorsal
ischial process; fibula <20% of tibia width.
There are also several characters also found in more derived birds, but not
Archaeopteryx- three distal quadrate condyles; expanded manual phalanx II-1;
no distinct posterior pubic foot.

> Protoarchaeopteryx is probably a very basal Oviraptorid, but not enough is
> known of it to say wether this is true or not, so it didn't have to have
had
> one in the first place.

I think it might be an enigmosaur, but Paul presents evidence it's an
archaeopterygid.

> Speeking of which, has there been any new studies concerning the
gastrolith
> Ornithomimid from Asia?

See http://www.cmnh.org/fun/dinosaur-archive/2001Oct/msg00253.html under
Kobayashi, Azuma, Dong and Barsbold, 2001. Bonebed of a new
gastrolith-bearing ornithomimid dinosaur from the Upper Cretaceous Ulansuhai
Formation of Nei Mongol Autonomous Region, China. JVP 21(3) 68A-69A.

Tim Williams wrote-

> I might be missing something, but the similarities shared by
Sinornithosaurus and
> Archaeopteryx are likely to be primitive eumaniraptoran traits.

That's how I feel about the characters shared by Sinornithosaurus and
dromaeosaurids (T-shaped quadratojugal, elongated distal caudal chevrons and
prezygopophyses and some others).

> Caudipteryx - the skull doesn't look equipped for a carnivorous diet, and
> there are gastroliths associated with the skeleton.  (Gastroliths suggests
> plant- or insect-eating... though I understand at least one allosaur [from
> Portugal] has them too.)

That's Lourinhanosaurus.  Syntarsus, Poekilopleuron and those new
ornithomimids have them too.

Mickey Mortimer