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Michael Teuton asks...
> I'm completely confused about Albertosaurus, Gorgosaurus, and other
> members of the Tyrannosauridae family. Which animals would have been
> contempories of T Rex? What's the family tree look like now?
Here's my take of the composition of the family Tyrannosauridae.
Only "true" tyrannosaurids are included - which is to say, those that
whose assignment to the family is not questioned by anyone (i.e
excluding _Alectrosaurus_, _Aublysodon_, _Shanshanosaurus_,
_Siamotyrannus_, _Stokesosaurus_ etc).
(?including _ G. sternbergi - possibly a species of smaller
tyrannosaurid, distinct from )libratus_)
(?incl. _A. arctunguis_ - possibly a distinct species, usually
regarded as a slender morph of _sarcophagus_).
_Maleevosaurus novojilovi_ - a pygmy tyrannosaurid from Asia. One
regarded as a juvenile _Tarbosaurus_, but Ken Carpenter showed
convincingly that it isn't.
"Chicagotyrannus chicagotyrannus" (also called the "stretch-snouted
_Daspletosaurus_) Includes a skull currently exhibited in the
Chicago Field Museum (under the name of _Albertosaurus_).
"The Rockies tyrannosaurid" - a new genus/species intermediate
between _Daspletosaurus_ and _Tyrannosaurus_. Comes from the Two
Medicine Formation, and currently housed in the University of the
Rockies (last I heard).
_Tarbosaurus bataar_ - Ken Carpenter regards this as a species of
_Tyrannosaurus_. George Olshevsky, however, discerns two separate
genera and species - _Tarbosaurus efremovi_ for a smaller version,
and _Jenghizkhan bataar_ for the larger one.
_Nanotyrannus lancensis_ - another pygmy tyrannosaurid, but looking
more and more like a juvenile _T. rex_.
_Dinotyrannus megagracilis_ - most people have grave doubts about
this one (it's based on a very fragmentary skeleton), but I think it's
And to answer your question Michael, only these last two are
contemporary with _T. rex_ (age: late Maastrichtian). _Albertosaurus_
material has also been reported from the late Maastrichtian, but I
doubt if its bona fide _Alberto_. Also contemporary with _T. rex_ is
_Stygivenator molnari_, a possible tyrannosaurid based on a
fragmentary skull still referred by some to _Aublysodon mirandus_.
As for the family tree... I think there's a paper (or two) coming out
soon which endevours to resolve the phylogeny of the Tyrannosauridae.
> Michael Teuton