Re: [dinosaur] Tyrannosaurus rex as an invasive species

[Gregory Paul <gsp1954@aol.com>]

Note that is very unlikely that Tyrannosaurus evolved in Asia and then headed east. The Bering land bridge had a pretty brutal climate -- even the summers were generally cloudy and chilly with temps rarely getting much above 60F due to the northern Pacific cold gyre, winters included blizzards, no reptiles present -- and the tyrannosaurid taxa from the North Slope appear to be a distinctive polar adapted forms. It is quite possible that Tyrannosaurus descended from a clade that had moved east from Asia including those polar forms. 

T. rex has not been documented to have existed from BC to Mexico. All the southern specimens are too fragmentary to even assign to the genus, they are indeterminate. And T. rex was probably restricted to the very last stage of the Lance and Hell Creek and Canadian formations all of which were laid down very shortly before the M/C boundary. Sue is probably not T. rex. Or Stan wherever that may be these days, or USNM 55555. 

To put it another way, stop chucking everything into T. rex. 

GSPaul

-----Original Message-----
From: Thomas Richard Holtz <tholtz@umd.edu>
To: Poekilopleuron <dinosaurtom2015@seznam.cz>
Cc: DML <dinosaur-l@usc.edu>
Sent: Fri, Feb 26, 2021 8:12 am
Subject: Re: [dinosaur] Tyrannosaurus rex as an invasive species

The rationale behind this is that Tyrannosaurus is more closely related to Tarbosaurus and Zhuchengtyrannus than it was to other North American tyrannosaurines. Furthermore, these Asian tyrannosaurinins are older than Tyrannosaurus. So the hypothesis is that this lineage of tyrannosaur originated in Asia, and the ancestor of Tyrannosaurus migrated into North America before the late Maastrichtian.

The spread isn't a problem: once a taxon makes it from one continent to another it can spread to the limits of its mobility and habitat in relatively quick periods. We see the same when Cenozoic mammals crossed Beringia either direction, or when they crossed the Isthmus of Panama.

On Fri, Feb 26, 2021 at 6:39 AM Poekilopleuron <dinosaurtom2015@seznam.cz> wrote:

Good day!

I would like to ask, if there is any support in the fossil record for the idea that a giant theropod Tyrannosaurus rex was actually an invasive species (migrating perhaps from Eastern Asia) that "flooded" North American ecosystems at the very end of the Cretaceous? Given that the fossils of this species are found thousands of kilometres away from each other (British Columbia to Mexico), that would make sense, perhaps? Thank you for your thoughts! Tom

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Thomas R. Holtz, Jr.
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