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Re: Re: Tyrannosaurs



>Here's a splitter's cladogram of Tyrannosauria I published in
>_Dino-Frontline_ #9 and 10, with a mistake or two corrected. Tyrannosauria is
>defined as a monophyletic suborder that includes all theropods with a
>didactyl manus. I expect disagreement with this, since the differences among
>the tyrannosaurids are subtle and in some workers' opinions insufficient for
>generic separation--not to mention the not-as-blue-sky-as-it-at-first-seems
>inclusion of _Compsognathus_ and didactyl-manus dino-birds. Numbered nodes
>are "branching" nodes--cladogenetic events, if you like; unnumbered nodes are
>monophyletic taxa not further split in the analysis.

In case anybody thought I'd be quiet on the subject, here's my ("lumpy")
cladogram of the Tyrannosauroidea.  I don't buy Dinogeorge's sister-group
relationship between Composgnathus and Tyrannosauroidea - other than
coelurosaur holapomorphies (basal synapomorphies) and the didactyl hands,
they don't share the derived features of the cranium, pelvis, hindlimb, and
tail that T. rex & kin share with the other advanced maniraptoriform
coelurosaurs.

Anyway, the sister taxa for Tyrannosauroidea would be (going from closest to
furthest out): the Bullatosauria (Ornithomimosaurs and Troodontids); Coelurus;
the oviraptorosaur-therizinosauroid clade; Maniraptora vera (birds and
dromeaosaurids).

I am unconviced as to the monophyly of the "Shanshanosaurinae" (formerly the
"Aublysodontinae").  These seem to be primitive tyrannosaurids for which the
only identified synapomorphy is the lack of serrations on the premaxillary
teeth.  Instead, I regard the "shanshanosaurines" as basal tyrannosaurids.

I am unconvinced that "Jenghizkhan" is a distinct genus.  On the word of one
of THE experts on tyrannosaurid skulls, I retain Maleev's original
assignment of the species "bataar" to the genus Tyrannosaurus.

As you'd expect of me, all groups below are monophyletic. 

Tyrannosauroidea
-Stokesosaurus
-Itemirus medullaris
-Tyrannosauridae
--Stygivenator molnari
--Shanshanosaurus huoyanshanensis
--Alectrosaurus olseni
--other "aublysodontine"/"shanshanosaurine" teeth and poscrania
--Tyrannosaurinae
---Alioramus remotus
---Maleevosaurus novojilovi
---Albertosaurus sarcophagus
---Daspletosaurus torosus
---Gorgosaurus libratus
---Nanotyrannus lancensis (may be juvenile T. rex)
---Dinotyrannus megagracilis (may be subadult T. rex)
---advanced tyrannosaurines
----Tarbosaurus efremovi
----Tyrannosaurus
-----Tyrannosaurus rex
-----Tyrannosaurus bataar

Unlike George (and some other paleontologists) I believe that a high degree of
intercontinental interchange occured during the Campano-Maastrichtian, so that
members of the same lineage (the advanced tyrannosaurines, the advanced
ankylosaurids (Euoplocephalus, Ankylosaurus, Talarurus, Dyoplosaurus), the
Edmontosaurini) and even the same genera (Tyrannosaurus, Saurolophus,
Velociraptor)
were found on both sides of Asiamerica.

Anyway, hope this helps.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist
Dept. of Geology
University of Maryland
College Park, MD  20742
Email:Thomas_R_HOLTZ@umail.umd.edu (th81)
Fax: 301-314-9661
Phone:301-405-4084