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Re: Coelurosaurian Relationships



Steve Brusatte wrote-

> This is probably one of the most important papers to date regarding
coelurosaurian relationships (at least one of the most important that I've
read).  Hopefully all of you who have ordered the Ostrom Symposium book have
received your copy, as this is a must-read.

If only I can get off my ass to order the thing :-)
I have been using their codings to help me fill in missing data in my
analysis though, especially with Pelecanimimus, Shuvuuia, Adasaurus,
"Ichabodcraniosaurus" and Achillobator.  It's great that they use
genus-level OTU's, I'm striving to do that too (I'm down to using only
Tyrannosauridae, Ornithomimidae, Oviraptoridae, Mononykinae, Troodontidae
and Ornithurae that are above genus level).  It does have its share of
errors (D-shaped premaxillary teeth in Dromaeosaurus and Utahraptor;
external naris not passing over antorbital fossa in Shuvuuia; maxillary
fenestra absent in Gallimimus (true?); etc.), but all data matrices do.
There are also many things coded differently from other analyses (like
Holtz's) that I'll have to ask about later onlist.

> Basically, the authors find a monophyletic Coelurosauria with the
tyrannosaurs as the closest outgroup.  The Ornithomimosauria is the sister
group to the Maniraptora.  Furthermore, the Maniraptora contains an
Alvarezsauridae subclade, which is a sister group to a bird-dromaeosaurid
clade and a troodontid-segnosaur-oviraptosaur clade.  The study also
supports a monophyletic grouping of segnosaurs and oviraptosaurs, although
the clade wasn't given a name (the paper was originally written back in 1999
or so, right?).  Furthermore, Dromaeosauridae is reconstructed as a possibly
paraphyletic taxon, although the authors acknowledge that missing data may
skew a possible monophyly, and the Bullatosauria is not supported.
>
> With that being said, I am curious about list reactions to this analysis.
Hopefully many of you have had a chance to read and digest this paper by
now.

My old analysis agreed that tyrannosauroids are more basal than
maniraptoriformes, with Maniraptora containing enigmosaurs and
eumaniraptorans (the dromaeosaurid + bird clade).  It was different in that
Ornitholestes was more basal than ornithomimosaurs, alvarezsaurids were more
derived than enigmosaurs, and troodontids were closer to eumaniraptorans
than enigmosaurs.  Other minor differences are that I placed Avimimus next
to alvarezsaurids, not caenagnathids; and that my oviraptorosaur topology
was
(Caudipter (Microven (Caenagn, Ovirapt))) not
(Caenagn (Microven (Caudipter, Ovirapt))) .

Their evidence for non-traditional clades is-
Maniraptora excluding Alvarezsauridae-
1. ossified sternal ribs
2. sternum with lateral processes
3. coracoid facet of sternum anteriorly placed
4. elongate coracoid
5. laterally facing glenoid
6. posterior trochantor
Troodontidae + Enigmosauria-
1. distinct rim on antorbital fossa
2. promaxillary fenestra absent
3. hollow basipterygoid processes
4. dentary subtriangular in lateral view
5. more than thirty dentary teeth
6. large serrations on teeth
7. proximodorsal lip on some manual unguals
Chirostenotes + Avimimus
1. ischium less than 66% of pubic length
2. arctometatarsalian
Microvenator + Caudipteryx + Oviraptoridae (excluding Chirostenotes)
1. all presacrals pneumatic (unknown but probable in Chirostenotes)
2. pubic shaft anterior concave (possibly not preserved in Chirostenotes due
to crushing)
3. no posterior trochantor
Caudipteryx + Oviraptoridae (excluding Microvenator and Chirostenotes)
1. anterior trochantor barely separated from greater trochantor
I have some thoughts on these characters, but don't have the time to analyze
them in depth right now.  I do think paravian troodontids and a (Caudip,
Microven (Caenag, Ovirap)) phylogeny are much better supported though.  The
alvarezsaurid thing?  Perhaps.  It's interesting to note that since 1999,
the AMNH team's tree has changed to make troodontids the sister group to
dromaeosaurids.

I think they should have included more basal taxa (Compsognathus, Scipionyx,
Coelurus, Nedcolbertia, Deltadromeus), some basal tyrannosauroids
(Stokesosaurus, Dryptosaurus), Bagaraatan, Protarchaeopteryx and Rahonavis.
Of course, many important taxa have been found since then that they couldn't
include (Eotyrannus, Nqwebasaurus, Sinosauropteryx [described well since
then at least], Beipiaosaurus, Nomingia, Microraptor, Bambiraptor,
Yandangornis).

Mickey Mortimer