Re: [dinosaur] Tarbosaurus and ancestry of Tyrannosaurus

Direct ancestry is always extraordinarily difficult to prove in the fossil record. The correct answer is "we don't know".

However, nearly all recent phylogenies put Tarbosaurus & Zhuchengtyrannus as closer to Tyrannosaurus than is Tarbosaurus. This doesn't clarify the place of origin, however, The next several branches out are North American. So it COULD be that the direct ancestry of Tyrannosaurus was North American, with a side branch migrating to Asia to become Tarbosaurus & Zhuchengtyrannus, But it could be that the common ancestry of Tyrannosaurus and the Asian forms was an Asian radiation, with Tyrannosaurus as a branch moving to America.

But here is a more important thing to think about: the dinosaurs wouldn't be experiencing "Asia" and "North America"/"Laramidia" as separate regions. They would have been effectively one continuous landmass. So it isn't always a legitimate approach to superimpose modern geographic concepts onto the paleogeography of the time.

I hope this helps,

On Wed, Jan 3, 2018 at 4:25 AM, Poekilopleuron <dinosaurtom2015@seznam.cz> wrote:

Good day,

I would like to known your opinion about what was probable direct ancestor of _T. rex_. Did it evolve from North American ancestor (like _Daspletosaurus torosus_) or rather from Asian immigrant species, like perhaps _Tarbosaurus bataar_? Thank you very much, Tom

Thomas R. Holtz, Jr.
Email:Âtholtz@umd.eduÂÂÂÂÂÂÂÂ Phone: 301-405-4084
Principal Lecturer, Vertebrate Paleontology

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