The new Tyrannosaurus species and competitors big and small paper

[Gregory Paul]

Hey everyone. What you have all been waiting for is now out! At long last paper #2 on the status of the TT-zone tyrannosaur genera and species. And this is not just about the big boys and girls, it deals with the small tyrannosaur remains too. The journal Mesozoic (no cost to publish long, open access studies:) paper is basically a big data and analysis dump to get the information out there that is needed for the community to proceed on the issues.

Gregory Paul (2025)

A presentation of the current data on the exceptionally diverse non-tyrannosaurid eutyrannosaur and tyrannosaurini genera and species of western North America during the End Cretaceous North American Interchange

Mesozoic 

https://doi.org/10.11646/mesozoic.2.2.1

pdf is a freebie

Enjoy. 

Part of this work builds upon Paul et al. (2022) to add a lot of new data that confirms there are multiple species of Tyrannosaurus. This includes new proportional data on the skulls, and most visibly on the postorbital display bosses that further distinguish the three species (the only major specimen to remain unidentified is good old 5027, poor dear lacks critical items, is intermediate in what it has, and stratigraphic level is underwater literally). In the process the actual appearance of T. rex is illustrated for the first time! We have all been getting it wrong -- until now. There is no way T. rex with its Mickey Mouse orbital bosses and T. imperator with its massive spindle bosses are the same species. There is nothing like such variation within any other tyrannosaurid species. Same goes for the proportional variations. Stop illustrating T. imperator and calling it T. rex, they could easily tell each other apart. Let's get real folks. 

A BIG I should have thought of it mistake I made in the 2022 paper was to not cite the 2020 Chure and Loewen paper naming A. jimmadseni with no phylogenetics, statistics, detailed stratigraphy, modest sample size and barely discussion the determination being pretty much in the diagnoses. And the paleocommunity made little fuss about that paper. Had I cited C & L in 2022 that may have tamped down the absurd massive negative reaction to the latter which was a mixture of paleopsychology and paleopolitics, it would have at least made it harder to be so paleohypocritical. 

The Longrich and Saitta paper last year -- which is favorable to multiple TT-zone Tyrannosaurus species as the opposition by the Trex Mafia (as per the Bomber Mafia of WW2 for those who get that) inevitably weakens -- got me to get into the issues with the lesser TT-zone tyrannosaurs. About a third of them are juvie Tyrannosaurus, they having the proper tooth counts, lack of a lateral dentary groove and the like. The rest are an array of nontyrannosaurids, at least some with hands as long or longer than adult Tyrannosaurus (all tyrannosaurids have the dinky arms) as Pete L presented over a dozen years ago, more teeth, lateral dentary grooves and other features that distinguish them not only from giant Tyranno, but from one another. It may be that the only Nanotyrannus lancensis specimen is the type which according to an 2024 SVP abstract is an adult. Jane might be in that genus, or maybe not. Stygivenator is valid, and Bloody Mary looks to be close to that but also different. Then there is good old Dryptosaurus, which may be late Maastrichtian. Could be some of the TT-zone remains belong to that taxon, at least at the genus level. Who knows. Just as we need to stop making Tyrannosaurus rex a wastebasket taxon that includes multiple species including gracile nontyrannosaurids, let's avoid making Nanotyrannus into another taxon trash can to chuck all the rest into. My analysis confirms L & S that Jane and Petey did grow like a juvenile Tyranno, they were subadults. Hopefully this paper will aid the Zanno crew in their work on Bloody Mary.  

The new Nature tyrannosaur paper came out too late to include in the main text, I added it to the Supplementary. Their claim that Nano is a baby Tyranno does not hold up. That an adult had dropped a tooth does not address the fact that Nano, Jane and probably BM had way too many teeth to be juvenile Tyranno -- tooth counts do not significantly decrease in growing reptiles that are not replacing the teeth with beaks -- all the more so when actual young Tyrannos have the same number of teeth as the grownups. There was wide variation in tooth count in juvenile Tyrannos and then they all ended up with the low adult count? What reptile does that happen in, much less tyrannosaurids? And Nano has the prominent lateral dentary groove absent in the juvenile and adult Tyrannosaurus. And the skull suturing and surface topography is too mature for an animal one half the length and one tenth the mass of the adults. And the 2024 SVP abstract indicates the hyoid bone ring count shows Nano is all grown up. So let's all grow up here. 

The TT-zone appears to be packed with a plethora of eutyrannosaur taxa, to a degree not seen elsewhere. Why? My most original notion is that the TT-zone gracile nontyrannosaurids were recent eastern immigrant stock that had migrated from Appalachia across the new land bridge, being relations of Dryptosaurus which had -- you guessed it -- big hands. That is the simple and straightforward hypothesis that finally explains the peculiar eutyrannosaur situation in the TT-zone. And these basal eutyrannosaurs that had evolved to be graciles were competing with the less gracile teen Tyrannosaurus that being compromise forms were having trouble with those pesky foreign immigrants taking up their space. Poor put upon growing Tyrannosaurus imperator, regina and rex. 

The Supplementary is very important because among other things it goes into extensive detail on why Carr 2020 does not come close to miraculously prebutting the Paul et al., but is also seriously defective in ways I did not fully understand until L & S. Really, proposing that growing T. rex for some reason underwent a fish like metamorphosis when no other tyrannosaurids does so, or for that matter any amniote? And some dinosaurologists went with that? And the invented growth curve? And the pretending that a decreasing tooth count in growing reptiles is normal? Or a highly variable tooth count in juveniles is also normal? The Supplementary also covers other important issues including the validity of assorted TT-zone type specimens.

Using Nano, Jane, Bloody Mary, Petey etc. to restore the ontogenetic development of Tyrannosaurus is about the same as using a lynx to do so with a puma, or a leopard for a lion or tiger, or Alioramus for Tarbosaurus. So stop doing that unless you have actual positive evidence they are juveniles. Use the actual juvenile Tyrannosaurus specimens -- which won't work well because they are all so fragmentary. 

Apparently the land bridge between east and west has never been named, so I call it Laralachia. Its location varies according to different maps, some have it near the US/Canadian border, others near the Gulf of Mexico. 

If you find the compression of specimen abbreviations and numbers -- AMNH 5027 to AMNH5027 -- annoying don't blame me, that was the editors. Wonder why I did not use the specimen # for Bloody Mary? Because the Dueling Dinosaurs have not been given catalog numbers, which is both odd and I think I know why.

Hopefully the response to this paper won't be over the top like last time. Partly because of the new data. Partly because of growing support in the literature. A number of paleos have told me they think the multispecies hypothesis is viable and should be treated seriously. 

Over at Wikipedia you folks get your butts in gear this time. When A. jimmadseni was named in the peer reviewed literature Wikipedia correctly immediately added it to its right box list of Allosaurus species despite the lack of above listed features in the paper. When A. anax was named on even less data same thing. And why is it that fragmentary T. macraeensis listed when that is controversial because it lacks some Tyrannosaurus features (especially posteroventral dentary) and its geoage is not tied down, but impera and regi based on much superior and better geoaged specimens are not? After being extensively diagnosed including via species identification display features in the peer reviewed literature T. regina and imperator are still not formally listed in the Wiki Tyrannosaurus entry. That should be immediately corrected of course. 

And folks knock off saying Tyrannosaurus rex on autopilot. It has always been bad paleoform to say that in a text that otherwise uses only generic titles, such as Triceratops, without the specific titles too such as horridus or prorsus, or Edmonotosaurus without annectens, and so on. Use T. rex only when discussing specimens that actually belong in that particular species. Or if you think they are one species defend the thesis -- can't just cite Carr et al. (2022) because this paper superseds that one. If you can't do that then just use Tyrannosaurus like you normally do Daspletosaurus, or Allosaurus, or Ceratosaurus, or..... See, it's easy.

GSPaul 

[Thomas Carr]

Hi Greg,

It isn't clear from the acknowledgements, but were there reviewers for this article?

Sincerely,

-TDC

[Gregory Paul]

Yes. Mesozoic is the same science press that runs Zootaxa, Zoosymposia, Phytotaxa, Megataxa, Bionomina, Palaeoentomology, Molluscan Research, Bulletin of Phylogenetic Nomenclature, Btyophyte Diversity and Evolution, Journal of Insect Biodiversity. 

So it's in the official PR literature:) Have fun! 

GSPaul

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[Thomas Carr]

Hey Greg,

Can you share who the reviewers were?

-TDC.

[Gregory Paul]

I don't know, it was anonymous as per usual. 

I did recommend people who have worked on tyrannosaurs, Currie, Longrich, Molnar, etc. But I did not see any indications in the reviews of their identities other than they knew about dinosaurs -- could have been people the editors selected ignoring my advice which is usually the case. We will never know. 

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[Gregory Paul]

And the reviews were extensive, a good deal of revising and adjusting. 

GSPaul

[Thomas Carr]

OK - good to know. (BTW there's some duplicated text on pages 99 - 101).

-TDC.

[Gregory Paul]

A note. I first submitted to Zootaxa, which I has run items on dinosaurs. But they said they were orienting to short items on new taxa for rapid publication. My paper was too long for that, and there are no new names in the paper. The sister publication Mesozoic does not have such limits -- and the same formatting so did not need to kill myself overhauling the paper:):):):) So no way I was not going to send it there. 

GSPaul

[Paul Penkalski]

Can you re-post the DOI link? This doesn't work, even if you add a period before pdf, or even if removing the whole pdf portion:

https://doi.org/10.11646/mesozoic.2.2.1pdf

Those pesky DOI links have to be exact. Thanks.

[Gregory Paul]

https://doi.org/10.11646/mesozoic.2.2.1

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