Nanotyrannus confirmed as distinct from Tyrannosaurus (article pending)

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

Big dinosaur news out today, confirming the validity of Nanotyrannus. For now, however, the link to the formal article in Nature is not working. 

Lindsay Zanno & James Napoli (2025)
Nanotyrannus and T. rex coexisted at the close of the Cretaceous
Nature (advance online publication)
DOI: 10.1038/s41586-025-09801-6
(Full article link pending…)


Tyrannosaurus rex ranks among the most comprehensively studied extinct vertebrates and a model system for dinosaur paleobiology. As one of the last surviving non-avian dinosaurs, Tyrannosaurus is a crucial datum for assessing terrestrial biodiversity, ecosystem structure, and biogeographic exchange immediately preceding the end-Cretaceous mass extinction —one of Earth’s greatest biological catastrophes. Paleobiological studies of Tyrannosaurus, including ontogenetic niche partitioning, feeding, locomotor biomechanics, and life history have drawn upon an expanding skeletal sample comprising multiple hypothesized growth stages—and yet the Tyrannosaurus hypodigm remains controversial. A key outstanding question relates to specimens considered to exemplify immature Tyrannosaurus, which have been argued to represent the distinct taxon Nanotyrannus. Here, we describe an exceptionally well-preserved, near somatically mature tyrannosaur skeleton (NCSM 40000) from the Hell Creek Formation that shares autapomorphies with the holotype specimen of N. lancensis. We couple comparative anatomy, longitudinal growth models, observations on ontogenetic character invariance, and a novel phylogenetic dataset to test the validity of Nanotyrannus, demonstrating conclusively that this taxon is distinguishable from Tyrannosaurus, sits outside Tyrannosauridae, and unexpectedly contains two species—N. lancensis and N. lethaeus, sp. nov. Our results prompt a re-evaluation of dozens of existing hypotheses based on currently indefensible ontogenetic trajectories. Finally, we document at least two co-occurring, ecomorphologically distinct genera in the Maastrichtian of North America, demonstrating that tyrannosauroid alpha diversity was thriving within one million years of the end-Cretaceous extinction.

****

Here are some of the news stories:

https://www.eurekalert.org/news-releases/1103512

https://www.theguardian.com/science/2025/oct/30/researchers-discover-nanotyrannus-tyrannosaur-species-in-duelling-dinosaurs-fossil

 
https://www.nytimes.com/2025/10/30/science/nanotyrannus-tyrannosaurus-rex-fossil.html

https://www.scientificamerican.com/article/nanotyrannus-isnt-a-juvenile-t-rex-its-a-separate-dinosaur/

https://www.sciencenews.org/article/nanotyrannus-not-teenaged-t-rex

[Ben Creisler]

It's now online as an unedited MS version:

Nanotyrannus lethaeus sp. nov.

Lindsay Zanno & James Napoli (2025)
Nanotyrannus and T. rex coexisted at the close of the Cretaceous

Nature (unedited advance online publication)
doi: https://doi.org/10.1038/s41586-025-09801-6
https://www.nature.com/articles/s41586-025-09801-6

Tyrannosaurus rex ranks among the most comprehensively studied extinct vertebrates and a model system for dinosaur paleobiology. As one of the last surviving non-avian dinosaurs, Tyrannosaurus is a crucial datum for assessing terrestrial biodiversity, ecosystem structure, and biogeographic exchange immediately preceding the end-Cretaceous mass extinction —one of Earth’s greatest biological catastrophes. Paleobiological studies of Tyrannosaurus, including ontogenetic niche partitioning, feeding, locomotor biomechanics, and life history have drawn upon an expanding skeletal sample comprising multiple hypothesized growth stages—and yet the Tyrannosaurus hypodigm remains controversial. A key outstanding question relates to specimens considered to exemplify immature Tyrannosaurus, which have been argued to represent the distinct taxon Nanotyrannus. Here, we describe an exceptionally well-preserved, near somatically mature tyrannosaur skeleton (NCSM 40000) from the Hell Creek Formation that shares autapomorphies with the holotype specimen of N. lancensis. We couple comparative anatomy, longitudinal growth models, observations on ontogenetic character invariance, and a novel phylogenetic dataset to test the validity of Nanotyrannus, demonstrating conclusively that this taxon is distinguishable from Tyrannosaurus, sits outside Tyrannosauridae, and unexpectedly contains two species—N. lancensis and N. lethaeus, sp. nov. Our results prompt a re-evaluation of dozens of existing hypotheses based on currently indefensible ontogenetic trajectories. Finally, we document at least two co-occurring, ecomorphologically distinct genera in the Maastrichtian of North America, demonstrating that tyrannosauroid alpha diversity was thriving within one million years of the end-Cretaceous extinction.

****

Lawrence M. Witmer (2025)
T. rex debate settled: contested fossils are smaller rival species, not juveniles
New evidence answers the question about whether some fossils are Tyrannosaurus rex juveniles or a different species, with implications for decades of published science.

https://www.nature.com/articles/d41586-025-03552-0

***

Katie Kavanagh (2025)
‘Teenage T. rex’ fossil is actually a different species
The discovery of smaller predator Nanotyrannus could prompt a re-think of tyrannosaur evolution.

https://www.nature.com/articles/d41586-025-03553-z

***
Video:

https://www.nature.com/articles/d41586-025-03561-z
=====

[Alex SciChannel]

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingG...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAMR9O1Ja4uU_iZBHr6DXh1iciWNiFkM%3DH9TEkaKFSZQRL8YdRw%40mail.gmail.com.

[Tyler Greenfield]

Unfortunately, the 'new family' 'Nanotyrannidae' is a nomen nudum. The authors fail to provide a character-based description/definition (they only have a phylogenetic definition) (ICZN Article 13.1) or an explicit indication of novelty (i.e., 'fam. nov.') (Article 16.1), rendering the name unavailable. Hopefully this issue will be fixed in the final, formatted version.

Along with the recent 'Alickmeron' debacle, this highlights that the major journals desperately need zoological nomenclature editors.

[Gregory Paul]

There is also the problem that the Nano holotype is a terrible type, it being only a skull with none of the vital postcrania. And it is missing much of the critical skull roof, and the skull is badly and oddly distorted, items that preclude doing a reliable dorsal view restoration. (The Carr 1999 version is plausible but cannot be verified. The aft portion is OK, he makes the snout broader than preserved which is probably correct but cannot be sure. So dorsal dimensions cannot be used to diagnose the taxon or for phylogenetic purposes as noted in my paper and Z&N. And Jane is missing the frontals and braincase.) We can exclude BM from being broadly contemporary Dryptosaurus because the latter has a very different arm and especially leg. Probably true for Jane too. But maybe Nano is a Drypto, there being no cross comparable material.  

The taxonomy of these things is very complicated and has difficulties, due to numerous differences and incomplete remains. 

GSPaul

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAL1L4F%2BTjb6n6pu_HX3nJSvua%3D0%2BAsjA1D4-yXGK4pun71wKiQ%40mail.gmail.com.

[Thomas Richard Holtz]

Nanotyrannidae may not follow ICZN rules, but it is a validly formed phylogenetic taxon name with a specific definition. The do not specify it as a "Family" in the Systematic Paleontology section.

That said, in terms of the ICZN it looks like it would be a potential junior synonym of Dryptosauridae, at least in those versions of their analyses where it forms a clade with Dryptosaurus to the exclusion of Tyrannosaurus. (Dryptosauridae has been used in some recent papers, particularly by Brownstein, as the clade encompassing Dryptosaurus and the Marshalltown taxon.)

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAL1L4F%2BTjb6n6pu_HX3nJSvua%3D0%2BAsjA1D4-yXGK4pun71wKiQ%40mail.gmail.com.

--

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

Office: CHEM 1225B, 8051 Regents Dr., College Park MD 20742

Dept. of Geology, University of Maryland
http://www.geol.umd.edu/~tholtz/

Phone: 301-405-6965
Fax: 301-314-9661              

Faculty Director, Science & Global Change Program, College Park Scholars

Office: Centreville 1216, 4243 Valley Dr., College Park MD 20742
http://www.geol.umd.edu/sgc
Fax: 301-314-9843

Mailing Address: 

                        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117

                        8000 Regents Drive
                        University of Maryland
                        College Park, MD 20742-4211 USA

[Ethan Schoales]

Thomas, do you agree with the paper’s overall conclusion.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAHQFgprkePZ3an4w%2BV%2BL48B1fntA4nsGSN_u5BgVYzRpU1A-WA%40mail.gmail.com.

[Tyler Greenfield]

'Nanotyrannidae' was clearly intended to be a family, given the -idae ending and the fact it was registered in ZooBank (which is only for ICZN-regulated names, not for unranked clades). It should also be noted that it doesn't meet the requirements of PhyloCode for phylogenetically-defined names either.

In terms of the ICZN, 'Nanotyrannidae' is not a synonym of anything because it is unavailable. Names have to be made available before they can be considered synonyms of other available names.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAHQFgprkePZ3an4w%2BV%2BL48B1fntA4nsGSN_u5BgVYzRpU1A-WA%40mail.gmail.com.

[Gregory Paul]

I just sent out this press notice to reporters, there are some alterations to this version --

REGARDING THE NATURE TYRANNOSAUR PAPER: THE “ESTABLISHMENT” WAS WRONG, GILMORE WAS RIGHT

 

In the wake of the work of Charles Gilmore, Peter Larson, Phil Currie, Bob Bakker, Nick Longrich, Evan Saitta, others, and myself, Zanno and Napoli are adding to the already overwhelming data that most of the small tyrannosaurs in the Tyrannosaurus-Triceratops (TT) zone are not juvenile Tyrannosaurus. 

 

Please understand that there has never been a true consensus in favor of the ETRH (everything is T. rex hypothesis), a radical idea first proposed by Thomas Carr in 1999 based on faulty data that the top tyrannosaur expert of our time, Phil Currie, corrected in 2003 but was then waved away. Contrary to what is the general storyline the burden of evidence is on the radical ETRH, not on the conventional Gilmore hypothesis. 

 

To wit, back in 1946 Gilmore at the Smithsonian (en.wikipedia.org/wiki/Charles_W._Gilmore#/media/File:Prof._Chas._Gilmore_of_Smithsonian_Institution_with_dinosaur_Diplodocus,_9-25-24_LCCN2016849560_(cropped).jpg; and no he did not star in horror movies;) was the first to recognize that Nanotyrannus lancensis (Gilmore named the species) was not a Tyrannosaurus, thereby firmly establishing the MTTH (multiple tyrannosaur taxa hypothesis), aka the Gilmore hypothesis. He did so using solid, straightforward, standard comparative reptile anatomy, ontogeny, and taxonomy which left no practical doubt on the issue. For one thing, Nanotyrannus simply has too many teeth to be Tyrannosaurus. Nothing fancy about it, it is as basic science as it gets -- reptile species almost always have stable tooth counts at any growth stage and very rarely lose teeth with maturity. In your articles please give good old Gilmore full credit for being the first to demonstrate the MTTH. 

 

Also deserving kudos in Peter Larson for his long advocacy of the MTTH, including the first analyses of Bloody Mary. 

 

The hyper gracile eutyrannosaurs probably evolved in Appalachia (as per Dryptosaurus and Appalachiosaurus) and migrated across the newly emerged Laralachia land bridge to Laramidia. I detailed this hypothesis in my Mesozoicpaper (8500 views,  https://doi.org/10.11646/mesozoic.2.2.1) which got no science news media coverage. Like Z&N the Mesozoic paper shows that the Nanotyrannus skull is too damaged to reliably compare to Tyrannosaurus. 

 

The Z&N work is in good accord with the Mesozoic paper. 

In 1999 Carr miscounted the teeth in growing Gorgosaurus and thought they declined in number with maturity. Four years later Currie, who in 1988 helped name Nanotyrannus, corrected that. At that point the ETRH should have been dropped. Instead in 2020 Carr proposed that growing Tyrannosaurus underwent a fish like metamorphosis, which never occurs in amniotes including reptiles. The ETRH was always the radical nonparsimonious hypothesis and never should have garnered so much attention. That so many opted for it was strange – it became the go-to but false paradigm running on preferred opinion rather than actual analyses -- and it has been repeatedly refuted for 80 years since the groundbreaking Gilmore paper and many others up until this year. The Z&N paper of course stands on the shoulders of others’ work.

 

The question never really has been if the MTTH is correct which it is. It is how many tyrannosaur taxa dwelled in the TT-both among the adult Tyrannosaurus, and the gracile basal eutyrannosaurs. 

GSPaul

[Thomas Carr]

Many thanks for the public thrashing.

To see where I was coming from regarding secondary metamorphosis, I recommend: Rose, CHRISTOPHER S., and JOHN O. Reiss. "Metamorphosis and the vertebrate skull: ontogenetic patterns and developmental mechanisms." The skull 1 (1993): 289-346.

Sincerely,

Thomas D. Carr, PhD

[Gregory Paul]

It is fab that the paper includes the entire cross-section of the femur so the growth rings can be directly measured from the center of the bone:) Unlike a lot of studies that don't include that:(

And finally the skeletal measurements! Looks like the skull is larger than that of Nano. Not sure can do a skeletal yet, specimen may still not be prepped enough. 

I am thinking their EDFIg 3a makes the skull a little short. I will have to work on that. Doing the dorsal view looks dicey. 

GSPaul

[Jaime Headden]

Each and every specimen said to be Tyrannosaurus rex was itself, a miraculous creation of the previous T. rex, sprung fully formed not from an egg, but from the cognitive, nay even predatory will of the collective Tyrannosaurus rex, as Athena leapt from the temple of Zeus. So it was that they antagonized one another, and leaving evidence not to the contrary, in which embattled primates argued and spewed such sophistry as this at one another, that they spent all that time ignoring the hyperpaedomorphic tyrannosaurins with which they deigned share territory with.

Ah, to have witnessed this cognitive birth, that we remain, with ample juvenile and subadult tyrannosaurins from the end-Cretaceous, not a whit of thought left to us that one, nor a fraction, nay, not even all, could possibly be a juvenile of the adult. It is time to call it what it is: the "Athena from Zeus" hypothesis, rather than the "Nanotyrannus must be real, please god, please make it so, it's my birthday today" hypothesis. For it cannot be but special pleading that every single non-adult tyrannosaurin from the end-Cretaceous is, in fact, a special pedomorphic adult. ONE OF THEM has to be a juvenile tyrannosaurin, and by extension of this logic, one of them HAS TO BE a juvenile Tyrannosaurus rex.

Cheers?

--

You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingG...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/934756551.1504537.1761859361430%40mail.yahoo.com.

--

Jaime A. Headden

The Bite Stuff: http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth" - P. B. Medawar (1969)

[Jaime Headden]

"indefensible ontogenetic trajectories" Is one hell of an argument.

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingG...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAMR9O1Ja4uU_iZBHr6DXh1iciWNiFkM%3DH9TEkaKFSZQRL8YdRw%40mail.gmail.com.

[Meig Dickson]

Meig Dickson reacted to your message:

---

From: dinosaurma...@googlegroups.com <dinosaurma...@googlegroups.com> on behalf of Jaime Headden <jaimeh...@gmail.com>
Sent: Thursday, October 30, 2025 9:36:16 PM
To: DinosaurMa...@googlegroups.com <DinosaurMa...@googlegroups.com>
Subject: Re: [DMG] Re: Nanotyrannus confirmed as distinct from Tyrannosaurus

 

WARNING This email originated external to the NMSU email system. Do not click on links or open attachments unless you are sure the content is safe.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAHyo4cRFfxD12nRaC5gRuKYTdR_67jWgm-ti1LKO-pSOZM3ccg%40mail.gmail.com.

[Jaime Headden]

Anyways,

Not to dig on the "Nanotyrannus must be real, please god, please make it so, it's my birthday today" hypothesis, but if the paper is sound, if it's phylogenetics, ontogenetic assessment, and so forth are sound, then we've a proper debate, not the spurious little interim things like "Nano is an albertosaurin because of the lateral vascular groove of the jaw" or something. But just like the argument of Triceratops vs Torosaurus, the debate largely ends when 1) you find an uncontroversial juvenile Tyrannosaurus rex, and 2) it's distinct from Nanotyrannus. Sound argumentation, solid evidence, and study replete with all the contravention required would be nice. I just don't like seeing "Indefensible ontogenetic trajectory" printed in an abstract unless we're talking about pseudoscience. I'm sure if we'd not seen the process itself, we'd have issues inferring that caterpillars are larval moths and butterflies, or that tadpoles are larval frogs. Indeed, at certain points in time, the juvenile has been considered *distinct* from the adults taxonomically for a large number of species; so much so that it's been wiser to err against nomenclature than for it.

Cheers,

[Gregory Paul]

Tom, that is fish and amphibians in the below paper. Not amniotes. The paper is actually a little miss titled in that regard. There is to the best of my knowledge no literature on metamorphosis in amniotes because it never occurs. That it does not is one of the key features of amniotes versus more basal vertebrates. 

I first became aware of this in Longrich and Saitta, so they were the first to point out a serious flaw in your 2020 paper. It should not have been offered up in the first place. We all make errors, best drop them when it becomes apparent.  

And there is no such thing in tyrannosaurs. As I illustrate in my summer paper with Tarbosaurus. As do Raun(?) et al. in the new 2025 SVP abstracts. 

An interesting item is that Tom continues to think Tarbosaurus is in Tyrannosaurus. Could well be if the two shared a fairly recent ancestor presumably in Asia (and of course, there is not really such a thing as Tarbosaurus bataar by ICZN rules, but that goes ignored except by Olshevsky and Ford). But all species within an amniote genus undergo pretty similar growth patterns. We know what that of Tarbosaurus is and it is entirely mundane ordinary, in amniote norms. If Tyrannosaurus is the same species it would have had a very similar ontegeny, markedly more so than to Gorgosaurus which also grew up normally but was left hefty. Put a restoration of the skeleton of super lithe Jane next to a bulky juv Tarbo of the same size and they are screamingly different. Because the former is not even a tyrannosaurid as Z&N, myself and L&S have shown. Cannot be both at the same time, Tyranno and Tarbo are the same genus (plausible) with super different ontogenies (not plausible).

As far as public trashing, that is what I and my companions got in spades in the wake of the 2022 paper in the international media by paleos for a paper that was the first to document the anatomical proportional differences in Tyrannosaurus not seen in the rest of the tyrannosaurids as a whole. No one else bothered to do that work. That when of late paper after paper has been publishing intragenera sibling species with similar or lesser evidence with no one blinking an eye. It is the Trex is special thing. And my Mesozoic paper that refutes Carr et al. 2022 and piles on more data, and said much of what is in Z&N was entirely ignored by the press (L&S did not get much coverage either for their ground breaking paper). And only one podcast came out that was hilariously wrong (said the data on femur robustness was invalid because no circumferance data was included cough cough among other things) and super snarky dismissive. Including showing a silly dancing girl when bashing one of my arguments, and showed a confused old man at another point. So am not particularly concerned. 

Since the 2000 the ETRH has been pushed as the sound, parsimonious, null consensus mainstream hypothesis, while those pointing out that it is actually a radical notion involving incorrect tooth counts and fish like growth was aggressively dismissed as being way out there, when the MTTH IS the parsimonious null hypothesis as per Gilmore 1946 who knew reptile anatomy. 

The problems have not been with the MTTH. 

GSPaul

--

You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingG...@googlegroups.com.
To view this discussion visit

https://groups.google.com/d/msgid/DinosaurMailingGroup/CANcgOPx%2B4v9U1d0tWjbCksyYdbb4UvQtyY8O9S8FdMCUe-Cw%2Bg%40mail.gmail.com

.

[Gregory Paul]

As I said in another post, there are about half a dozen actual juvenile Tyrannosaurus specimens known, some illustrated in Fig. 8 in https://doi.org/10.11646/mesozoic.2.2.1. Among other Tyrannosaurus features they lack a prominent lateral dentary groove. 

GSPaul

https://groups.google.com/d/msgid/DinosaurMailingGroup/CAHyo4cSNoa76FM4KLGNdK8i%3D4XnCB0hnAM07WRdxc6qEzt%3Db1g%40mail.gmail.com

.

[Thomas Carr]

"Secondary metamorphosis" was the term that best describes the pattern that I thought the data showed (a rapid, wholesale change in skull and dentition morphology in two years or less). Rather than coining a new term, I thought it best to use a useful, clear term that was already in use. The clades don't really matter, but the phenomenon does; I was making a claim of analogy, not homology.

Also, the claim of secondary metamorphosis is a falsifiable hypothesis in that it can be tested by new fossils that fill the gap between juveniles and young adults. So I thought (and still do think) that the term and the hypothesis have scientific value in their descriptive utility and testability.

If I must be called out as a fool (or stupid) for that, then OK fine.

-DC.

[Thomas Carr]

Yes, but - as I said in another post - the question of true juvenile rexes is in the context of Z&N's hypothesis, not of previous work.

-TDC

[Gregory Paul]

Got too many items on my plate at the moment to look into this item at this time, I will have to see what Z&N did regarding this it being a potentially notable issue. 

GSPaul

On Thursday, October 30, 2025 at 06:32:00 PM EDT, 'Thomas Carr' via Dinosaur Mailing Group <dinosaurma...@googlegroups.com> wrote:

Yes, but - as I said in another post - the question of true juvenile rexes is in the context of Z&N's hypothesis, not of previous work.

-TDC

--

You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingG...@googlegroups.com.
To view this discussion visit

https://groups.google.com/d/msgid/DinosaurMailingGroup/CANcgOPxcp4EANeRGmFBnKB_4%3D0NRYdKL%3DZHW-7tnURoUzK01Qg%40mail.gmail.com

.

[Gregory Paul]

Tom the press notice does not all you a fool. Here are the passages in which you are mentioned. 

"Please understand that there has never been a true consensus in favor of the ETRH (everything is T. rex hypothesis), a radical idea first proposed by Thomas Carr in 1999 based on faulty data that the top tyrannosaur expert of our time, Phil Currie, corrected in 2003 but was then waved away. Contrary to what is the general storyline the burden of evidence is on the radical ETRH, not on the conventional Gilmore hypothesis. 

 

In 1999 Carr miscounted the teeth in growing Gorgosaurus and thought they declined in number with maturity. Four years later Currie, who in 1988 helped name Nanotyrannus, corrected that. At that point the ETRH should have been dropped. Instead in 2020 Carr proposed that growing Tyrannosaurus underwent a fish like metamorphosis, which never occurs in amniotes including reptiles. The ETRH was always the radical nonparsimonious hypothesis and never should have garnered so much attention. That so many opted for it was strange – it became the go-to but false paradigm running on preferred opinion rather than actual analyses -- and it has been repeatedly refuted for 80 years since the groundbreaking Gilmore paper and many others up until this year." 

The above are accounts of what happened, and my and others opinions on them, some in the technical literature. 

You did in the 1999 paper publish incorrect tooth counts for growing Gorgosaurus that gave the impression that ontogenetic tooth loss did happen in the clade. I wonder if the 15 teeth for AMNH 5664 was from Bakker et al. 1988 because I assume it is Dr Bob who got it wrong there. It was a mistake, there are such items in my publications. In 2003 Phil refuted the data. That removed what is a critical argument for the ETRH, it became that for some reason T. rex very rarely among amniotes and not among other tyrannos including its close buddy Tarbosaurus lost teeth. (If instead Tarbo did undergo a strinking shift then the Carr hypothesis would be applicable to its N Amer cousin). The idea should have been dropped, or at best considered the nonparsimonous alternative to the Gilmore hypohesis that it is. 

to put it another way, had I suggested something like that I would have caught heck. Never would have been accepted in the PRL. And we all know that is true. 

Nor is there any actual data that Tyrannosaurus grew differently than other reptiles tyrannosaurids included, so no need to offer an atypical growth scheme not seen in other amniotes. Larson and others had been pointing to the actual juv Tyrannosaurus specimens for years. 

Related to that, if all the half size TT-zone tyrannosaurs are thrown into the T. rex pot, then there is amazing variation in the juveniles. Tooth counts from 11-17 I think, some with more robust teeth, some with prominent lateral dentary grooves and other without, lots of proportional and other cranial shape differences, some with tibias about the same length as the femur and others with much longer shanks. And then the differences winnow down in adults with 11-13/14 teeth opposite reptilian norm, dentary groove consistently weak at best, skulls pretty similar overall (but not those wild and wacky Tyrannosaurus postorbital bosses:). Is there any case in which juveniles are more variable than their parents? Does not intraspecies variation remain low at all growth stages, or increase with growth? 

As for being gone after in public, in the NYTimes article on the Paul et al. 2022 paper Carr said that the evidence in the paper was "vanishingly weak" (I kept the print copy) in a piece read by millions around the world. Which if someone said about a paper by Carr he would consider being called a fool it seems. That about a paper that was the first to show that femoral robustness in Tyrannosaurus varies more (when size adjusted) than all other tyrannosaurids combined, that the gracile Tyrannosaurus are off the main tyrannosaurid line with all others being comparatively robust (Scott found that out), that all the gracile are high in the TT-zone so it is stratigraphically correlated, that are good stratigraphic trend patterns for other features including the dentary teeth, and so forth. Had such data been used to name species of some within an other dinosaur genus it would have been considered normal. What should have happened was folks should have said interesting paper, breaks new ground on the most popular dinosaur no one else had been working on, see how things play out down the line. But no, T. rex is just so special. So our ground breaking paper was truly and often gleefully trashed. 

Until 2010 I had not thought much about Tyrannosaurus species. After the Scannella Triceratops species talk at SVP thought it would be a good idea to look into Tyrannosaurus, no one else did. Published the results and got harshly treated for daring challenge the very special status of the tyrant lizard king. That was neither scientific nor professional. And now the ETRH has been yet further undercut by another paper. And I am pointing out it is not the MTTH that is critically doubtful, but the ETRH. Them's the breaks. 

GSPaul   

--

You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingG...@googlegroups.com.
To view this discussion visit

https://groups.google.com/d/msgid/DinosaurMailingGroup/CANcgOPwOkO-NdUYHjykFy-GqA9gi0b%3DnyC4b054-R1djrkm_eg%40mail.gmail.com

.

[Thomas Carr]

Yes, but, have I clarified the secondary metamorphosis issue to your satisfaction?

-TDC

[Sean McKelvey]

Yeah, is it entirely necessary to turn this into a "such and such was right and such and such was wrong, haha" situation?

The one problem I have with this paper is that, as expected, it's turned into a parade of gloating and thinly veiled spite for other workers.

How about we treat this professionally instead of making it a (pardon my French) p*****g contest?

On Fri, 31 Oct 2025 at 09:56, 'Thomas Carr' via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com> wrote:

Yes, but, have I clarified the secondary metamorphosis issue to your satisfaction?

-TDC

--

You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingG...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CANcgOPyZ9a1v9QVJDYPwW-BWNdBN31vJ5mQibpAQ54VEfsHP%3DQ%40mail.gmail.com.

[Ethan Schoales]

Do people agree with the paper’s conclusions, though?

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CACHaABF6XmMNxTxUx4r--i12emyRCy3jL%3DutCbkTX7QJ9WJrSw%40mail.gmail.com.

[Gregory Paul]

I do with most of it;)

GSPaul

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CALAi95EW1Rs8LmvNFQs%2BSfvvpkPcnN90uWxP0%3D3vGPJaT-cGtg%40mail.gmail.com.

[Sean McKelvey]

I don't disagree with the conclusions, I just don't see why people on one side of the "debate" have to start with the "told you so". 

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CALAi95EW1Rs8LmvNFQs%2BSfvvpkPcnN90uWxP0%3D3vGPJaT-cGtg%40mail.gmail.com.

[Ethan Schoales]

Of course Greg already thought Nanotyrannus was separate from Tyrannosaurus, so did the paper newly convince anyone?

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/493203225.1556357.1761878546955%40mail.yahoo.com.

[Sean McKelvey]

Me. I was firmly on the side of it being a young Tyrannosaurus. But I really can't argue with the results of this paper, nor am I really qualified to do so anyway.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CALAi95HckpGya6UvPQ-ZdQpnwgGFnVOvi8t5f-Rqzojxv_vUFQ%40mail.gmail.com.

[Sean McKelvey]

My main questions now are;

1. What exactly do we have in regards to true juvenile Tyrannosaurus

2. I'm interested to see how exactly Dryptosaurus fits into this, Are we confident Nanotyrannus is not just Dryptosaurus?

[Gregory Paul]

Because Nano lacks postcrania and Drypto has barely any skull their being the same genus or species cannot be ruled out. Nano is the only TT-zone tyrannosaur that might be Drypto. but that is not particularly likely. Need postcrania that can be confidently assigned to Nano to know better. 

GSPaul

https://groups.google.com/d/msgid/DinosaurMailingGroup/CACHaABGMknUt2t-tO2jp6vOBC4zWfZc-LsRjqKMzMSKudAb05Q%40mail.gmail.com

.

[Sean McKelvey]

Makes sense, thanks for clearing that up.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/949732020.1556544.1761879710987%40mail.yahoo.com.

[Tim Williams]

Sean McKelvey <smc...@gmail.com> wrote:

> Me. I was firmly on the side of it being a young Tyrannosaurus. But I really can't argue with the results of this paper, nor am I really qualified to do so anyway.

Me as well.  But it's good to have _Nanotyrannus_ back.  No such luck for _Stygivenator_ (regarded by Zanno & Napoli as a nomen dubium).

> My main questions now are;
> 1. What exactly do we have in regards to true juvenile Tyrannosaurus

GSP listed a bunch of specimens.  This includes LACM 23845 (the _Albertosaurus megagracilis_ holotype), mentioned in the Supplementary Information as a juvenile _T. rex_.  Although GSP also lists "KU156375" as a juvenile _Tyrannosaurus_, Zanno & Napoli refer this specimen to _Nanotyrannus lancensis_.

[Jura]

For reference and somewhat in defense of GSP, the anti-Nanotyrannus crowd has been very vocal about it for the past twenty or so years, ranging from tongue-in-cheek humour in places like SVP and PaleoFest, to outright vitriol in the online paleophile communities. 

So, a little bit of gloating from the other side seems justified.

[dayne schwarz]

I have remained neutral on this subject for some time, because I can understand the points from both sides that were either confident in the validity of the species and with those who inherently believed it was a juvenile Tyrannosaurus Rex. But from what I’ve gathered from the material presented for the subject, I think there is enough evidence to suggest Nanotyrannus as a legitimate species. This is exciting news! So I’m looking forward to hearing more about the research and the potential Ontogenetic implications this will present to the Tyrannosauroidea family. 

Dayne Schwarz,

Undergraduate Student, Earth Sciences

Brock University 

St. Catharines, Ontario

On Thursday, October 30, 2025, Sean McKelvey <smc...@gmail.com> wrote:

Makes sense, thanks for clearing that up.

To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingGroup+unsub...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CANcgOPyZ9a1v9QVJDYPwW-BWNdBN31vJ5mQibpAQ54VEfsHP%3DQ%40mail.gmail.com.

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.

To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingGroup+unsub...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CACHaABF6XmMNxTxUx4r--i12emyRCy3jL%3DutCbkTX7QJ9WJrSw%40mail.gmail.com.

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.

To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingGroup+unsub...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CALAi95EW1Rs8LmvNFQs%2BSfvvpkPcnN90uWxP0%3D3vGPJaT-cGtg%40mail.gmail.com.

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.

To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingGroup+unsub...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/493203225.1556357.1761878546955%40mail.yahoo.com.

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.

To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingGroup+unsub...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CALAi95HckpGya6UvPQ-ZdQpnwgGFnVOvi8t5f-Rqzojxv_vUFQ%40mail.gmail.com.

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.

To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingGroup+unsub...@googlegroups.com.

To view this discussion visit

https://groups.google.com/d/msgid/DinosaurMailingGroup/CACHaABGMknUt2t-tO2jp6vOBC4zWfZc-LsRjqKMzMSKudAb05Q%40mail.gmail.com

.

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.

To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingGroup+unsub...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/949732020.1556544.1761879710987%40mail.yahoo.com.

--

You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.

To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingGroup+unsub...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CACHaABG%3DH%3DG2i86VfSivTYeE4goCS4Xe-zJJ4u2DFim0xdmBew%40mail.gmail.com.

[Gregory Paul]

I am rechecking KU 156375 and it looks like one of the young Tyrannosaurus, not sure why Z&N put it in Nano yet. Z&N do not otherwise consider the low tooth count etc Tyrannosaurus juveniles. So they do not put every lesser specimen outside the genus leaving it without any kids. 

Stygivenator is a bad specimen. But it is not a Nanotyrannus, and neither is BM. And as noted earlier Nano itself is a problem holotype. Z&N are correct that Jane is not the same taxon as that. 

GSPaul

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingG...@googlegroups.com.
To view this discussion visit

https://groups.google.com/d/msgid/DinosaurMailingGroup/CA%2BnnY_EcYEWDM5qV5yJvge6k8QCXrbQaAhLhgM2e%3DBk__Eu0dQ%40mail.gmail.com

.

[Gregory Paul]

What can be done on the ontogeny of the Tyrannosaurus species is pretty limited. Although there are a few juvenile specimens as I have noted today (from the Mesozoic paper), they are all not all that good. So no nice growth series of good specimens like Gorgosaurus and Tarbosaurus. We do know that like the latter Tyrannosaurus juveniles were more on the robust side, and seem to have had a short tibia. But cannot do in-depth comparisons until better Tyrannosaurus youngsters show up. Might be better to stick to Gorgo and Tarbo for that.

GSPaul 

On Thursday, October 30, 2025 at 11:45:01 PM EDT, dayne schwarz <daynesc...@gmail.com> wrote:

I have remained neutral on this subject for some time, because I can understand the points from both sides that were either confident in the validity of the species and with those who inherently believed it was a juvenile Tyrannosaurus Rex. But from what I’ve gathered from the material presented for the subject, I think there is enough evidence to suggest Nanotyrannus as a legitimate species. This is exciting news! So I’m looking forward to hearing more about the research and the potential Ontogenetic implications this will present to the Tyrannosauroidea family. 

Dayne Schwarz,

Undergraduate Student, Earth Sciences

Brock University 

St. Catharines, Ontario

On Thursday, October 30, 2025, Sean McKelvey <smc...@gmail.com> wrote:

Makes sense, thanks for clearing that up.

To view this discussion visit https://groups.google.com/d/ msgid/DinosaurMailingGroup/ CACHaABF6XmMNxTxUx4r-- i12emyRCy3jL% 3DutCbkTX7QJ9WJrSw%40mail. gmail.com.

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingGroup+ unsub...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/ msgid/DinosaurMailingGroup/ CALAi95EW1Rs8LmvNFQs% 2BSfvvpkPcnN90uWxP0%3D3vGPJaT- cGtg%40mail.gmail.com.

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingGroup+ unsub...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/ msgid/DinosaurMailingGroup/ 493203225.1556357. 1761878546955%40mail.yahoo.com .

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingGroup+ unsub...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/ msgid/DinosaurMailingGroup/ CALAi95HckpGya6UvPQ- ZdQpnwgGFnVOvi8t5f-Rqzojxv_ vUFQ%40mail.gmail.com.

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingGroup+ unsub...@googlegroups.com.
To view this discussion visit

https://groups.google.com/d/ msgid/DinosaurMailingGroup/ CACHaABGMknUt2t- tO2jp6vOBC4zWfZc- LsRjqKMzMSKudAb05Q%40mail. gmail.com

.

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingGroup+ unsub...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/ msgid/DinosaurMailingGroup/ 949732020.1556544. 1761879710987%40mail.yahoo.com .

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingGroup+ unsub...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/ msgid/DinosaurMailingGroup/ CACHaABG%3DH% 3DG2i86VfSivTYeE4goCS4Xe- zJJ4u2DFim0xdmBew%40mail. gmail.com.

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.

To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingG...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAFaR-50xC%3Ds5nM%3DqyKv69zge78GSoh4wK243EOVRxQu31rrYBA%40mail.gmail.com.

[Sean McKelvey]

I'm VERY interested to see what further work can be done regarding this subject, I'm sure more interesting little details will gradually reveal themselves.

I also have my fingers crossed that we can find some more complete and useful fossils from young Tyrannosaurus for comparison's sake. 

Wouldn't hurt to have some better material from Dryptosaurus as well.

Hopefully we can get both in due time.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/726207355.1570874.1761882679420%40mail.yahoo.com.

[Sean McKelvey]

As for the gloating on the Nano side, while I understand the reasoning behind it, two wrongs don't make a right. It would be quite easy to simply take the high road here and not descend into the same kind of silliness the other side of the debate did.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/644b0f06-6c67-4210-b917-f6c9832faa43n%40googlegroups.com.

[Ben Creisler]

Some additional items:

Videos:

We Ended the Greatest Debate in Paleontology... James Napoli
Skeleton Crew
19 min.

https://www.youtube.com/watch?v=Y5EB6zcrCOU

***

Nanotyrannus Resurrection: Two Species, New Evidence #Nanotyrannus #Nanotyrannus Debate
Fossil Crates
8 min.

https://www.youtube.com/watch?v=IK6zom7nYo0

====

News: 

Nanotyrannus Confirmed: Dueling Dinosaurs Fossil Rewrites the Story of T. rex

https://naturalsciences.org/calendar/news/nanotyrannus-confirmed/

****
'I was wrong': Dinosaur scientists agree that small tyrannosaur Nanotyrannus was real, pivotal new study finds

https://www.livescience.com/animals/dinosaurs/i-was-wrong-dinosaur-scientists-agree-that-small-tyrannosaur-nanotyrannus-was-real-pivotal-new-study-finds

****

Scientists thought this fossil was a teen T. rex. Turns out it's a new tyrannosaur

https://www.npr.org/2025/10/30/nx-s1-5589172/tyrannosaurus-rex-dueling-dinosaurs-fossil-new-species

On Thu, Oct 30, 2025 at 11:18 AM Ben Creisler <bcre...@gmail.com> wrote:

It's now online as an unedited MS version:

Nanotyrannus lethaeus sp. nov.

Lindsay E. Zanno & James G. Napoli (2025)

[Stephen Poropat]

“We ended the greatest debate in palaeontology…”

If this was the greatest debate left in palaeontology, then the barrel’s bottom is within scraping distance. Maybe it’s true if you define “palaeontology” as “the study of Cretaceous theropods of North America”…

Hyperbole, I know, and only a headline, probably written by someone other than James Napoli. But I lament that this is what some modes of science “communication” have to resort to for clicks.

Dr Stephen F. Poropat

Deputy Director

Western Australian Organic and Isotope Geochemistry Centre

School of Earth and Planetary Sciences

Curtin University

Bentley, Western Australia

Australia 6102

https://stephenporopat.weebly.com/

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingG...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAMR9O1Kvf465F6%3DJbajBvjMMeEtC6wDrB5RD-HRxUtZnwyNJiA%40mail.gmail.com.

[Jaime Headden]

Personally, how cute and in what relation to vertebrates conodonts lie is a much more interesting debate, or the whole 3v4 "domains" of life debate that raged for upwards of a century (and which, sadly, still goes on).

Cheers,

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAPf2Mx7COfARXARf3LF6U-9rD7SrCbHKc8gSEyq236_P9PiG0A%40mail.gmail.com.

[Sean McKelvey]

Have to agree with you there. Unfortunately, this is where we seem to be in regards to sci-comm. 

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAPf2Mx7COfARXARf3LF6U-9rD7SrCbHKc8gSEyq236_P9PiG0A%40mail.gmail.com.

[Tim Williams]

Gregory Paul wrote:

>  (and of course, there is not really such a thing as Tarbosaurus bataar by ICZN rules,

Umm... what?  It's only because of ICZN rules that we have _Tarbosaurus bataar_ at all.

As you know, _Tyrannosaurus bataar_ was named before _Tarbosaurus efremovi_.  When the two species were synonymized, this led to the new combination _Tarbosaurus bataar_, due to the Principle of Priority - a point made by Hurum and Sabath (2003).  (Unfortunately, Maleev misspelled the Mongolian word _baatar_, 'hero', - as used in so many multituberculate genera.)

> but that goes ignored except by Olshevsky and Ford)

Not at all sure what you mean here.  Here's what Olshevsky and Ford (1995) had to say:

"I resurrect _Tarbosaurus efremovi_ as a distinct Asian genus and species, and make
the giant _Tyrannosaurus bataar_ the type species of the new genus _Jenghizkhan_..."

Olshevsky and Ford (1995) went a bit hog-wild with new tyrannosaurid names.  As well as _Jenghizkhan_, they also came up with _Stygivenator_ and _Dinotyrannus_.

[Sean McKelvey]

Hog wild maybe, but I'd be lying if I said I didn't think Jengizkhan was an excellent name for a Mongolian Tyrannosaur.

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingG...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CA%2BnnY_HKnV6XEBZ37XssZQmcxPeyGe7gGnuiKXE8wZFs71jJfg%40mail.gmail.com.

[Stephen Poropat]

Similar thing happened with Eromangasaurus australis. Sachs named it Styxosaurus australis in 2005, later in 2005 Kear named the same specimen Eromangasaurus carinognathus. Eventually resolved by Kear 2007: the accepted combination is Eromangasaurus australis.

Dr Stephen F. Poropat

Deputy Director

Western Australian Organic and Isotope Geochemistry Centre

School of Earth and Planetary Sciences

Curtin University

Bentley, Western Australia

Australia 6102

https://stephenporopat.weebly.com/

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CACHaABFJKA4STf5munMPRtjK_0GwhFFHXS3LY8rcuWLLAr6%3DZQ%40mail.gmail.com.

[Tim Williams]

Sean McKelvey <smc...@gmail.com> wrote:

> Hog wild maybe, but I'd be lying if I said I didn't think Jengizkhan was an excellent name for a Mongolian Tyrannosaur.

Yes, I have to agree with you there.  But unlike the Mongol conqueror himself, the name _Jengizkhan_ went absolutely nowhere.  One could question whether this new genus was needed at all - as is the case for the other names.  The three genera were published in a Japanese magazine about dinosaurs - still counts as validly published under the ICZN.  

Purely from a nomenclature standpoint, I like the name _Stygivenator_ - especially the use of the Latinized combining form of Styx (which refers to the Hell Creek Formation).

The name _Dinotyrannus_ is meh.  Also somewhat tautological ("terrible tyrant").

[Gregory Paul]

I concur. 

Although it is of course about the science in the end. The modern ETRH which started only a quarter century ago has never been a sensible idea. Yet it became widely popular in much of the establishment who then thrashed those who dared disagree with what became the T. rex Mafia (after the Bomber Mafia of WW2, look it up). Which was not a good idea because it was always readily subject to refutation. Which may be a reason why so many became way over defensive about it, typical psychology. And there is that T. rex is just so very special thing. 

Bad combination. 

Paleos are people too. 

GSPaul

https://groups.google.com/d/msgid/DinosaurMailingGroup/644b0f06-6c67-4210-b917-f6c9832faa43n%40googlegroups.com

.

[Gregory Paul]

True, but do not hold one's breath. More out of the limited exposure New Egypt Formation is not likely to pop up in the next hundred years. Who knows when a definite Nanotyrannus with skeleton will be found. Well over a century and no good actual juvenile Tyrannosaurus yet sad to say, that could continue for a good while. 

GSPaul

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CACHaABH0PxzgOB9iEiP_GDk2E-jZ%2BFOhw3LJmEHK4vJ4mrO_XQ%40mail.gmail.com.

[Isaac Wilson]

Greg, I'm curious to hear your reasoning behind Bloody Mary not being a Nano as established by Zanno and Napoli. Is it simply due to the preservation issues with the N. lancensis holotype? 

Isaac

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/1769237235.1608618.1761913035669%40mail.yahoo.com.

[Gregory Paul]

The sentiment is understandable. But there is a false equivalence here. The attitude of the T. rex Mafia was not merely an intimidation campaign, but it was based on a deeply faulty hypothesis. Had it actually been the superior hypothesis at least the snark would have been scientifically justified. The MTTH is the ordinary, null hypothesis based on your run of the mill comparative anatomy and normal amniote reptilian ontogeny. And became even more so when it was shown that alioramians lived with tarbos, so what is the big deal with baso-eutyrannosaurs dwelling along with Tyrannosaurus. And there are multiple species of Daspletosaurus that are actually not all that difference which is expected in intragenera sibling species, so why not a bunch of Tyrannosaurus species in the TT-zone? After they having been put upon for so long for no good reason complaining about the MTTH clique having some fun is not fun. 

GSPaul

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CACHaABHdvSg418iMjOXHKQXbTsLYAb698g4vkotVBu21enC7%2Bg%40mail.gmail.com.

[Gregory Paul]

You can check Fig. 8 in https://doi.org/10.11646/mesozoic.2.2.1. It's obvious they are very distinct taxa. I am doing a new BM skull restoration based on the Z&N photos, but the earlier was based on good pics and it will not be dramatically different. And there is the diagnoses in that paper. 

GSPaul

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAM_kBJHU5xLr7LCYrHa2xWviitcD1t18gF6v6_z%3D_-m7OV5e_g%40mail.gmail.com.

[Gregory Paul]

Oops, sorry. That is Fig. 10 that compares the skulls. 

[Gregory Paul]

I think we are taking a fundamentally cross purposes here. Not exactly sure how however, so cannot fully address the disagreement. In any case it is not just me, Z&N disagree very strongly with the idea, as did L&S a couple of years ago (prior to that I had been so focused on the grownup species thing that I had not noticed the metamorphosis premise). So I am not the only one that would need to be satisfied on the issue. You will have to present a good explanation ultimately in the literature if you wish to continue to promote the concept, but they may be a dead hypothesis.  

GSPaul

On Thursday, October 30, 2025 at 07:56:49 PM EDT, 'Thomas Carr' via Dinosaur Mailing Group <dinosaurma...@googlegroups.com> wrote:

Yes, but, have I clarified the secondary metamorphosis issue to your satisfaction?

-TDC

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.

To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingG...@googlegroups.com.
To view this discussion visit

https://groups.google.com/d/msgid/DinosaurMailingGroup/CANcgOPyZ9a1v9QVJDYPwW-BWNdBN31vJ5mQibpAQ54VEfsHP%3DQ%40mail.gmail.com

.

[Mickey Mortimer]

Well, the family situation could have been worse. From Naish's part of the peer review file- "Taxonomy and phylogenetic definition. Any ‘family-level’ group anchored on Nanotyrannus cannot be ‘Nanotyrannosauridae’ because there is no ‘Nanotyrannosaurus’: it must instead be Nanotyrannidae. As precedent, the authors may not be aware that there is an extant dinosaur family based on Tyrannus (kingbirds), namely Tyrannidae. Use of ‘Nanotyrannosauridae’ and ‘nanotyrannosaurids’ later in the ms (lines 516-531, Fig. 5) needs to be changed in view of this."

I'll also raise my usual objection of a priori excluding taxa- "For all parsimony analyses, Nanuqsaurus hoglundi and Dynamoterror dynastes, which are known from only very fragmentary material107,108, acted as wildcards and were pruned from our analyses a priori."

More confusingly- "We also constrained a monophyletic Proceratosauridae (Guanlong + Yutyrannus), following universal recognition of this clade in tyrannosauroid matrices." First of all, not so. The original description used Carr's famous matrix and found Yutyrannus in Pantyrannosauria. But even if it were true, Yutyrannus is such a new taxon only preliminarily described in a tabloid, I don't think a proceratosaurid identity is crucial in the least, certainly not enough to constrain it. Makes me curious if letting Yutyrannus do its thing had some unwanted effect on the topology elsewhere, especially since all the maximum parsimony trees had Juratyrant and Stokesosaurus as proceratosaurids, which I don't think has been recovered before.

But in general a very convincing paper - Nanotyrannus is not Tyrannosaurus. Consider my mind changed.

Mickey Mortimer

[Ryan Benjamin]

I get some interesting results when running the maximum parsimony analysis (with implied weighting) without constraints, in that proceratosaurids, Compsognathus, Zuolong, and Dilong all end up in Allosauroidea (also Alectrosaurus ends up in Albertosaurinae, but that's quite as odd). To be fair, the contents of Proceratosauridae remain the same despite the change in position, so Yutyrannus and "stokesosaurids" being proceratosaurids does seem to be genuine rather than solely the result of the constraints.

[Gregory Paul]

I had Proceratosaurus and Ornitholestes with allosaurs back in PDW. 

GSPaul

https://groups.google.com/d/msgid/DinosaurMailingGroup/e524c02f-53a6-49fe-851d-5c0a6d6f7d83n%40googlegroups.com

.

[Mickey Mortimer]

Ryan Benjamin wrote- " I get some interesting results when running the maximum parsimony analysis (with implied weighting) without constraints, in that proceratosaurids, Compsognathus, Zuolong, and Dilong all end up in Allosauroidea (also Alectrosaurus ends up in Albertosaurinae, but that's quite as odd). To be fair, the contents of Proceratosauridae remain the same despite the change in position, so Yutyrannus and "stokesosaurids" being proceratosaurids does seem to be genuine rather than solely the result of the constraints."

Well the authors do constrain the positions of non-tyrannosauroids too- "we constrained our tree searches to enforce an outgroup topology following recent studies of Averostra, with Majungasaurus as the ultimate outgroup, Monolophosaurus and Dubreuillosaurus diverging basal to Carnosauria (Allosaurus spp., Sinraptor, and Acrocanthosaurus), and Zuolong and Compsognathus as successive proximal outgroups to Tyrannosauroidea." Which I think is just fine because their analysis I assume only uses characters meant for Tyrannosauroidea, so this way you don't have to clog it up with characters supporting Coelurosauria, Avetheropoda, Tetanurae, etc. just to get the 'right' distribution of character states among the outgroups. So those taxa becoming allosauroids when unconstrained is not surprising because they're all only being evaluated in a tyrannosauroid matrix. It's one of Peters' problems and reasons his results are so bad- his characters were designed with basal amniotes so of course dinosaurs, mammals and such aren't going to be analyzed usefully. The same thing happens in my Lori matrix, where the characters were all chosen because they vary in maniraptoromorphs, so once you get outside Averostra you get really weird results despite the number and accuracy of scores.

To truly test my question, could you keep all the constraints EXCEPT Proceratosauridae?

Mickey Mortimer

[Tim Williams]

Jaime Headden <jaimeh...@gmail.com> wrote:

> Personally, how cute and in what relation to vertebrates conodonts lie is a much more interesting debate,

The origin of flight in insects is at the top of my list.  Flight is the major reason for the phenomenal success of insects - and, in turn, a major contributor to the dominance of flowering plants.  

> or the whole 3v4 "domains" of life debate that raged for upwards of a century (and which, sadly, still goes on).

As someone who has skin in the game, the debate is now centered on 2 vs 3 domains of life.

[Thomas Yazbek]

It's interesting that paleoentomology is so obscure given how important extant insects are in our time. 

T. Yazbeck

--

You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingG...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CA%2BnnY_H3RoWv1hpDWM4ZtPFYv51jAfYtx_9t3RTTyFncL96zxA%40mail.gmail.com.

[Grant Hurlburt]

Has anyone a pdf of "Dodson, P. 1975. Functional and ecological significance of relative growth in Alligator. J. Zool. 175, 315–355 "? Many thanks in advance.

Grant Hurlburt

On Thu, Oct 30, 2025 at 1:36 PM Ben Creisler <bcre...@gmail.com> wrote:

Ben Creisler

bcre...@gmail.com

Big dinosaur news out today, confirming the validity of Nanotyrannus. For now, however, the link to the formal article in Nature is not working. 

Lindsay Zanno & James Napoli (2025)
Nanotyrannus and T. rex coexisted at the close of the Cretaceous
Nature (advance online publication)
DOI: 10.1038/s41586-025-09801-6
(Full article link pending…)


Tyrannosaurus rex ranks among the most comprehensively studied extinct vertebrates and a model system for dinosaur paleobiology. As one of the last surviving non-avian dinosaurs, Tyrannosaurus is a crucial datum for assessing terrestrial biodiversity, ecosystem structure, and biogeographic exchange immediately preceding the end-Cretaceous mass extinction —one of Earth’s greatest biological catastrophes. Paleobiological studies of Tyrannosaurus, including ontogenetic niche partitioning, feeding, locomotor biomechanics, and life history have drawn upon an expanding skeletal sample comprising multiple hypothesized growth stages—and yet the Tyrannosaurus hypodigm remains controversial. A key outstanding question relates to specimens considered to exemplify immature Tyrannosaurus, which have been argued to represent the distinct taxon Nanotyrannus. Here, we describe an exceptionally well-preserved, near somatically mature tyrannosaur skeleton (NCSM 40000) from the Hell Creek Formation that shares autapomorphies with the holotype specimen of N. lancensis. We couple comparative anatomy, longitudinal growth models, observations on ontogenetic character invariance, and a novel phylogenetic dataset to test the validity of Nanotyrannus, demonstrating conclusively that this taxon is distinguishable from Tyrannosaurus, sits outside Tyrannosauridae, and unexpectedly contains two species—N. lancensis and N. lethaeus, sp. nov. Our results prompt a re-evaluation of dozens of existing hypotheses based on currently indefensible ontogenetic trajectories. Finally, we document at least two co-occurring, ecomorphologically distinct genera in the Maastrichtian of North America, demonstrating that tyrannosauroid alpha diversity was thriving within one million years of the end-Cretaceous extinction.

****

Here are some of the news stories:

https://www.eurekalert.org/news-releases/1103512

https://www.theguardian.com/science/2025/oct/30/researchers-discover-nanotyrannus-tyrannosaur-species-in-duelling-dinosaurs-fossil

 
https://www.nytimes.com/2025/10/30/science/nanotyrannus-tyrannosaurus-rex-fossil.html

https://www.scientificamerican.com/article/nanotyrannus-isnt-a-juvenile-t-rex-its-a-separate-dinosaur/

https://www.sciencenews.org/article/nanotyrannus-not-teenaged-t-rex

--
You received this message because you are subscribed to the Google Groups "Dinosaur Mailing Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to DinosaurMailingG...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/CAMR9O1JNYuRE_8mOtdx%2BCdfnL%3D7P%2B5hyVQU7iauH4Uy%3D%3DcHrDQ%40mail.gmail.com.

--

Grant Hurlburt

[Jerry Harris]

Here's the Alligator growth paper.

[Grant Hurlburt]

Thanks very much, Jerry

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/a0e124b0-ded4-4e69-9fd4-977bfda38fd4n%40googlegroups.com.

--

Grant Hurlburt