When is a T-rex not a T-rex? When it's
Tyrannosaurus bataar.
Tyrannosaurus is the
type genus of the superfamily
Tyrannosauroidea, the
family Tyrannosauridae, and the subfamily Tyrannosaurinae; in other words it is the standard by which paleontologists decide whether to include other species in the same group. Other members of the tyrannosaurine subfamily include the North American
Daspletosaurus and the
Asian Tarbosaurus,
[66][67] both of which have occasionally been synonymized with
Tyrannosaurus.
[29][
page needed] Tyrannosaurids were once commonly thought to be descendants of earlier large theropods such as
megalosaurs and
carnosaurs, although more recently they were reclassified with the generally smaller
coelurosaurs.
[28]
Diagram showing the differences between a generalized
Tarbosaurus (A) and
Tyrannosaurus (B) skull
In 1955, Soviet
paleontologist Evgeny Maleev named a new species,
Tyrannosaurus bataar, from
Mongolia.
[68] By 1965, this species had been renamed
Tarbosaurus bataar.
[69] Despite the renaming, many
phylogenetic analyses have found
Tarbosaurus bataar to be the
sister taxon of
Tyrannosaurus rex,
[67] and it has often been considered an Asian species of
Tyrannosaurus.
[28][70][71] A recent redescription of the skull of
Tarbosaurus bataar has shown that it was much narrower than that of
Tyrannosaurus rex and that during a bite, the distribution of stress in the skull would have been very different, closer to that of
Alioramus, another Asian tyrannosaur.
[72] A related
cladistic analysis found that
Alioramus, not
Tyrannosaurus, was the sister taxon of
Tarbosaurus, which, if true, would suggest that
Tarbosaurus and
Tyrannosaurus should remain separate.
[66] The discovery and description of
Qianzhousaurus would later disprove this and revealed that
Alioramus belonged to the clade
Alioramini.
[73][74] The discovery of the tyrannosaurid
Lythronax further indicates that
Tarbosaurus and
Tyrannosaurus are closely related, forming a clade with fellow Asian tyrannosaurid
Zhuchengtyrannus, with
Lythronax being their sister taxon.
[75][76] A further study from 2016 by Steve Brusatte, Thomas Carr et al., also indicates
Tyrannosaurus may have been an immigrant from Asia, as well as a possible descendent of
Tarbosaurus. The study further indicates the possibility that
Tyrannosaurus may have driven other tyrannosaurids that were native to North America extinct through competition.
[77] Other finds in 2006 indicate giant tyrannosaurs may have been present in North America as early as 75 million years ago. Whether or not this specimen belongs to
Tyrannosaurus rex, a new species of
Tyrannosaurus, or a new genus entirely is still unknown.
[78]
LOL.
