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Re: Albertosaurus

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).

_Gorgosaurus libratus_
(?including _ G. sternbergi - possibly a species of smaller 
tyrannosaurid, distinct from )libratus_) 

_Albertosaurus sarcophagus_
(?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.

_Daspletosaurus torosus_

"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).

_Tyrannosaurus rex_

_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.

Tim Williams

> Michael  Teuton