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Re: I'm back...



David Marjanovic wrote-

> - Is it possible that I have found, in the famous illustrations, a
> synapomorphy for Arctometatarsalia: a rugose crest in the midline on the
> nasals? Do troodontids have such a thing (ornithomimo- and tyrannosaurs
do,
> dromaeosaurs don't, neither do oviraptorosaurs primitively)?

This is a really hard character to code.  Even among tyrannosaurids,
juveniles and Alectrosaurus (GIN 100/50) lack rugose nasals (does this
indicate the referred Alectrosaurus material is juvenile?).  Eotyrannus has
a median ridge anteriorly and lots of large and small foramina, but I don't
think it's rugose.  I know Paul gives ornithomimids little rugose midline
nasal ridges like tyrannosaurids, but you'd be hard-pressed to find this in
the literature.  Neither Osmolska et al. (1972) or Russell (1972) illustrate
anything of the sort for Gallimimus and Dromiceiomimus respectively (though
Osmolska et al.'s drawings were inaccurate in other ways (Hurum, 2001), so
this may not mean much).  Regarding troodontids, both Byronosaurus and
Saurornithoides mongoliensis appear to have smooth nasals.  While that of
Saurornithoides junior looks textured in my bad photocopy, it's not rugose
in the way tyrannosaurids' are as far as I can tell.

> - Is it possible that likewise a strongly reduced maxilla and strongly
> enlarged premaxilla (I'll quantify later :-) , I mean that the biting
force
> has shifted from maxilla to premaxilla, a prerequisite for prokinesis) is
a
> synapomorphy for a group that contains only Oviraptorosauria, Segnosauria,
> *Avimimus* and Metornithes?

Well, both Caudipteryx and oviraptorids have a premaxilla taking up about a
third of the ventral jaw margin.  For comparison, that of dromaeosaurids
takes up 20-23%.  We can't tell in Avimimus until someone determines the
snout length.  Erlikosaurus has a normally-sized premaxilla (24% of jaw
margin), while that of Shuvuuia is really small (<10% of jaw margin), so
they wouldn't count.  The ratio in pygostylians varies quite a bit (40% in
Confuciusornis; 30% in Eoenantiornis; 25% in the Spanish nestling; 29% in
Cathayornis; >50% in Gobipteryx; 48% in Yanornis; 52% in Hesperornis).  You
might be able to get this to work for an oviraptorosaurian synapomorphy
(though their short snouts may be a big influence), or a pygostylian
synapomorphy, accepting a few reversals (Cathayornis? caudatus and
Cuspirostrisornis also appear to have small premaxillae).  But if you're
including segnosaurs and such, reversals would abound.

> - I had totally forgotten the drawing of an *Avimimus* skull. Terribly
> birdlike -- orbit and lower temporal fenestra are confluent, the jugal has
> no ascending process. This occurs in Alvarezsauridae (*Mononykus* and
> *Shuvuuia*) and Ornithothoraces (don't know for *Jibeinia*, *Longipteryx*
> and *Protopteryx*, but nowhere else among dinosaurs. May this support the
> traditional content of Metornithes and a reversal (due to reinforcing the
> skull for ?leaf-eating) in confuciusornithids?

Here's a commonly made error- ornithothoracines do have ascending processes
on their jugals, at least until the Ornithurae.  Both the Spanish
enantiornithine nestling and the basal euornithine Yanornis have an
ascending process.  What may be the jugal (else it's a surangular) in
Liaoxiornis expands posteriorly, perhaps suggesting an ascending process was
present here too.  Other enantiornithines with preserved skulls don't have
the proper area preserved (Eoenantiornis, Cathayornis, etc.).  The fact
Shuvuuia and Avimimus both have this is one of the characters that makes me
think they form a monophyletic group, but I'll wait until all my characters
have been verified until I'll officially support it.  Lack of
postorbital-jugal contact could indeed support a Metornithes if reversed in
Confuciusornis.  Archaeopteryx may also have this character, although it is
currently debated.  Ever notice Bambiraptor has only a point contact between
the bones?  Might be an intermediate condition, or they may not have touched
in life, as the skull was disarticulated.  The condition's unknown in
Sinornithosaurus, NGMC 91 and Microraptor, so this character may be more
widespread than previously thought.

> Regarding the BCF debate -- _plenty_ of Jurassic dromaeosaurid teeth,
> including Early Jurassic ones from Antarctica, have been discussed onlist
at
> length for years, besides MJ and LJ troodontid teeth, LJ ornithomimosaur
> teeth + a finger, LJ tyrannosaur teeth (apart from LJ *Stokesosaurus* and
> maybe MJ *Iliosuchus*), LJ oviraptorosaur vertebrae and so on. Oh, and EJ
> and LT bird tracks. I don't know how far beyond doubt any of these are,
but
> apparently there are lots of them. What we need is of course something
like
> Messel or the sites in Liáoníng of Middle Jurassic age... :.-(

Keep in mind the Antarctic teeth come from a single post from Tracy,
nothing's been published yet.  The Middle Jurassic "troodontid" tooth really
doesn't look like a troodontid to me.  Something more like Richardoestesia
perhaps....  I'm still waiting for your evidence of Late Jurassic
ornithomimosaur teeth.  The Morrison cervical vertebrae are not
oviraptorosaurian, they are from a basal member of the
segnosaur-oviraptorosaur clade.  But yes, plenty of Late Jurassic
coelurosaurs and a few Middle Jurassic ones too.

Mickey Mortimer