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Re: Tyrannosaurid Growth Spurts
John Hunt wrote:
BTW, has Gorgosaurus been re-instated, I thought it was a synonym for
Based on two recent studies, yes, _Gorgosaurus libratus_ and _Albertosaurus
sarcophagus_ appear to represent distinct genera:
Currie, P.J., Hurum, J.H., and Sabath, K. (2003). Skull structure and
evolution in tyrannosaurid dinosaurs. Acta Palaeontologica Polonica 48 (2):
Hurum, P.J. and Sabath, K. (2003). Giant theropod dinosaurs from Asia and
North America: Skulls of Tarbosaurus bataar and Tyrannosaurus rex compared.
Acta Palaeontologica Polonica 48 (2): 161-190.
Overall, the Tyrannosauridae have undergone a taxonomic implosion in recent
years. The current consensus is that _Tyrannosaurus_, _Tarbosaurus_,
_Gorgosaurus_, and _Alectrosaurus_ are valid genera. (This may change once
the type material for _Alectrosaurus_ is re-studied.) _Shanshanosaurus_,
_Maleevosaurus_ and _Jenghizkhan_ are likely junior synonyms of
_Tarbosaurus_, with the first two representing early ontogenetic stages of
_Tarbosaurus_. Likewise, _Aublysodon_, _Stygivenator_ and_Dinotyrannus_ are
considered junior synonyms of _Tyrannosaurus_, with these genera
representing early ontogenetic stages of _Tyrannosaurus_.
The jury is still out on the validity of _Nanotyrannus_ and _Alioramus_.
_Nanotyrannus_ is undoubtedly based on a young tyrannosaur specimen (not an
adult specimen of a "dwarf" tyrannosaur taxon); but this specimen may not be
referrable to _Tyrannosaurus_. _Alioramus_ is also probably based on a
juvenile specimen, and is provisionally regarded as distinct from
There are also some more basal tyrannosaur genera (_Eotyrannus_,
_Stokesosaurus_, _Aviatyrannus_, possibly _Iliosuchus_), as well as
_Itemirus_, which shows both dromaeosaur and tyrannosaur-like features.
_Dryptosaurus_ and perhaps even _Bagaraatan_ may also belong somewhere in
the tyrannosaur clade. As for_Siamotyrannus_, recent phylogenies have
pushed this taxon further down the Theropoda tree, closer to (or among) the
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