what do you think of Paul (2025)?

[Giggino Demente]

dear paleontologists of the mailing group, I would be very curious to know your opinion on the latest paper by Paul (who is also present in the group). Is it a good paper or a not so good paper? thank you very much

[Franco Sancarlo]

I have never personally done papers on tyrannosaurids but I am very curious about them and I have read enough papers on the subject. Paul's paper is excellent, probably the best on the subject. Very good in almost everything, even if it has some typos and some parts I honestly did not like

Il Mar 1 Lug 2025, 02:17 Giggino Demente <gigginod...@gmail.com> ha scritto:

dear paleontologists of the mailing group, I would be very curious to know your opinion on the latest paper by Paul (who is also present in the group). Is it a good paper or a not so good paper? thank you very much

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[Tim Williams]

I'm keeping an open mind.

Certain assertions in the paper make me uneasy.  For example, this one:

"Teeth can be lost in favour of a beak during a major ontogenetic shift from juvenile predation to adult herbivory (Wang et al., 2017), this is not pertinent to the consistently predaceous tyrannosaurs."

_Limusaurus_ (the subject of Wang et al. 2017) shows us that extreme ontogenetic changes can occur in theropods - in this case, that teeth were completely lost from the jaws and replaced by a toothless beak.  The craniodental changes required to get from a _Nanotyrannus_ morphology to a _Tyrannosaurus_ morphology are far less extreme than those observed in _Limusaurus_.  

In _Limusaurus_ (and others, see doi.org/10.1073/pnas.170802311) the loss of teeth is coupled to the development of a beak.  But there is no reason to assume or assert that ontogenetic tooth loss could not occur for different reasons in other theropods.  

Along this same theme, there is the following hyperbole:

"The myth of tooth loss being normal in avepods is incorrect and never should be repeated unless actual evidence to the contrary is produced."

AFAIK, no one is claiming that tooth loss is "normal" in avepods.  But claiming that it can never happen (except when associated with a beak) is entirely unfounded, and strikes me as _ex cathedra_.  

(The Supplementary Text also asserts that there are "numerous lines of evidence against significant tooth reduction in reptile ontogeny", despite the fact that it does actually happen.)

Another reservation I have is that the paper mentions certain characters deemed to be of "phylogenetic importance".  But there is no phylogenetic analysis.  In this context, this particular statement is odd:

"MS (T). If the above forms of evidence for juvenile status of small individuals of a clade are substantial or better, the greater the phylogenetic remoteness from the adult members of the clade the greater the probability of
the former not being juveniles of the latter."

What is this "phylogenetic remoteness"?  And how would it be quantified?

Cau's 2024 paper 'A Unified Framework for Predatory Dinosaur Macroevolution' (available at www.researchgate.net/publication/379902868) would seem to be relevant to both ontogenetic disparity in theropods and its potential impact on phylogenetic placement.  But it's not cited.

On Tue, Jul 1, 2025 at 10:17 AM Giggino Demente <gigginod...@gmail.com> wrote:

dear paleontologists of the mailing group, I would be very curious to know your opinion on the latest paper by Paul (who is also present in the group). Is it a good paper or a not so good paper? thank you very much

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[Giggino Demente]

Tim thanks for the reply, but otherwise what was the paper like in your opinion?

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[Gregory Paul]

On Tuesday, July 1, 2025 at 12:06:25 AM EDT, Tim Williams <tij...@gmail.com> wrote:

(The Supplementary Text also asserts that there are "numerous lines of evidence against significant tooth reduction in reptile ontogeny", despite the fact that it does actually happen.)

My assertion was based in part on the extensive study by Brown et al. (2015). Please cite examples (either TW, or anyone else), preferably in the technical literature,  in which growing reptiles past or present consistently lose two or more teeth (aside from loss of teeth in favor of a beak). And examples of reptiles that as juveniles have significantly differing tooth counts, and as adults end up with much less variation. 

GSPaul  

[Jura]

Rieppel and Labhardt (1979) discuss the surprising changes that occur in the mandibular teeth of Varanus niloticus during ontogeny. Tooth shape changes drastically, but so far as I can see the tooth count either doesn't change or it slightly increases. Estes and Williams (1984) did a more comprehensive review on the ontogeny of molariform, "crushing" teeth in lizards and noted similar examples of tooth shape changing through development, though again with no specific mention of tooth loss.

Refs

Estes, R. and Williams, E.E. 1984. Ontogenetic variation in the molariform teeth of lizards. Journal of Vertebrate Paleontology, 4(1):96-107.

Rieppel, O. and Labhardt, L. 1979. Mandibular mechanics in Varanus niloticus (Reptilia: Lacertilia). Herpetologica 35(2): 158-163.

Jason

[Gregory Paul]

Interesting. Yes, tooth form can change in reptile onteogeny, as per some dinosaurs. But no record of tooth count changes so far. 

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[Gregory Paul]

I should modify this to significant consistent drops in counts. Increases, in rare cases dramatic, do occur. 

GSPaul

[Tim Williams]

Giggino Demente <gigginod...@gmail.com> wrote:

> Tim thanks for the reply, but otherwise what was the paper like in your opinion?

TBH, I still haven't fully read through it.  Which brings me to one thing about the paper that could have been improved: it's too long (especially the supp text... hoo boy). 

So far, it hasn't convinced me that _T. regina_ and _T. imperator_ are valid species (i.e., not synonyms of _T. rex_).  But that's just me.  Though maybe something is up with certain specimens (e.g., BMRP  2002.4.1 / Jane).

[The Dinosaur Heretic]

Maybe I’m missing something here, but if these Nanotyrannus/Stygivenator specimens were to undergo a rapid shift from sleek and long-legged to robust brutes, would it not stand to reason that the number of dentary teeth would stay the same throughout their ontogeny?

For example, based on CT scans of the dentary, CMNH 7541 has 16 dentary teeth. Losing teeth in favour of a beak is such a dramatic shift in Limusaurus because of a significant change in niche; from omnivore to herbivore. If CMNH 7541 were to grow up to full size, then the change in niche from medium-sized pursuit predator to large ambush predator is nowhere near as significant, therefore not validating a change in tooth count. The way I see it, a fully grown CMNH 7541 would retain its 16 dentary teeth (this is just a hypothetical and impossible to validate, but it remains consistent with the notion that reptiles don’t lose teeth as they age, except for in extreme circumstances. I wouldn’t consider T. rex ontogeny to be particularly extreme, and especially not compared to Limusaurus).

The most amount of dentary teeth I’ve seen in T. rex is 14 (Scotty, AMNH 5027, B-rex, etc.), so I don’t think it’s out of the realm of possibility that a T. rex dentary shows up with 16 dentary teeth, especially when the tooth count is already as variable as it is. Jane - BMRP 2002.4.1 - features 14 dentary teeth, which is consistent with the max. number of dentary teeth in T. rex specimens collected thus far.

Getting stuck on tooth counts just doesn’t seem worthwhile to me.

In my view, the only compelling case for Nanotyrannus or another tyrannosaur coexisting with T. rex lies in Bloody Mary. Until it’s published, I remain Switzerland.

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[Giggino Demente]

really interesting, but instead regarding the boss part? the bosses of T.regina seem too variable

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[Giggino Demente]

T.regina  seem to be too variable 

[Gregory Paul]

On Wednesday, July 2, 2025 at 02:16:13 AM EDT, The Dinosaur Heretic <thedinosa...@gmail.com> wrote:

Maybe I’m missing something here, but if these Nanotyrannus/Stygivenator specimens were to undergo a rapid shift from sleek and long-legged to robust brutes, would it not stand to reason that the number of dentary teeth would stay the same throughout their ontogeny?

>Yes, as is true in all reptiles, including the other tyrannosaurids which also grew up from graceful to brutish.  

For example, based on CT scans of the dentary, CMNH 7541 has 16 dentary teeth. Losing teeth in favour of a beak is such a dramatic shift in Limusaurus because of a significant change in niche; from omnivore to herbivore. If CMNH 7541 were to grow up to full size, then the change in niche from medium-sized pursuit predator to large ambush predator is nowhere near as significant, therefore not validating a change in tooth count. The way I see it, a fully grown CMNH 7541 would retain its 16 dentary teeth (this is just a hypothetical and impossible to validate, but it remains consistent with the notion that reptiles don’t lose teeth as they age, except for in extreme circumstances. I wouldn’t consider T. rex ontogeny to be particularly extreme, and especially not compared to Limusaurus).

>The data indicates 7541 was full size or close to it -- Gilmore saw that in 1942 and the new data confirms that -- but if it were a juvenile it would retain a lot of teeth when adult.  

The most amount of dentary teeth I’ve seen in T. rex is 14 (Scotty, AMNH 5027, B-rex, etc.), so I don’t think it’s out of the realm of possibility that a T. rex dentary shows up with 16 dentary teeth, especially when the tooth count is already as variable as it is. Jane - BMRP 2002.4.1 - features 14 dentary teeth, which is consistent with the max. number of dentary teeth in T. rex specimens collected thus far.

> Jane has more teeth than that, see Fig 8G in the paper.   

Getting stuck on tooth counts just doesn’t seem worthwhile to me.

> Gilmore did not even think of putting Nano in Tyrannosaurus partly because the tooth count automatically excludes it from being in the same genus. That is basic taxonomic comparative biology. He was in full accord with the parsimonious null hypothesis. As were Bakker et al. 1988,  that pesky Paul dude same years, and Peter L all along. 

In the paper that got the nonparsimonious notion that everything inthe TT-zone is Trex and don't attention to the detailed implausible osteological differences that requires was Carr 1999. In which he incorrectly claimed that tooth counts were variable and declined with age in Gorgosaurus. No they are not and don't. Had that boo-boo not occurred then the extraordinary ETRH may not have arisen, and there would be no controversy about Nano, Jane, Bloody Mary, Stygi, Petey not being Tyrannosaurus. 

The tooth counts are of critical importance they being basic osteological comparative taxonomic osteological anatomy. They disprove the ETRH as Gilmore understood back in WW 2.  

In my view, the only compelling case for Nanotyrannus or another tyrannosaur coexisting with T. rex lies in Bloody Mary. Until it’s published, I remain Switzerland.

On Wed, 2 Jul 2025 at 3:15 pm, Tim Williams <tij...@gmail.com> wrote:

Giggino Demente <gigginod...@gmail.com> wrote:

> Tim thanks for the reply, but otherwise what was the paper like in your opinion?

TBH, I still haven't fully read through it.  Which brings me to one thing about the paper that could have been improved: it's too long (especially the supp text... hoo boy). 

So far, it hasn't convinced me that _T. regina_ and _T. imperator_ are valid species (i.e., not synonyms of _T. rex_).  But that's just me.  Though maybe something is up with certain specimens (e.g., BMRP  2002.4.1 / Jane).

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[Gregory Paul]

Display features can vary in a species, ontogeny of course, and sexes. The point is that the spindles are seen only in low TT-zone robust T. imperator that retains the normal tyrannosaurid two dentary incisors, the Mickey Mouse discs only in robust high placed T. rex which looks a lot different than we all realized, and the gracile T. regina lacked either of those, even on big Stan. So there is a solid correlation that is expected in multiple species. And the variation in Tyranno is far in excess of that seen in other tyrannosaur species, and within other tyrannosaurs combined for that matter. These being one species is thus very nonparsimonious.

GSPaul

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[Giggino Demente]

thank you very much for the explanations, but I heard from the paleontologist Andrea Cau that the number of teeth decreases with growth, at least that's what he told me on Facebook

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[Gregory Paul]

I have heard something about Cau's post which may be the only comment by a professional dinosaurologist on the Mesozoic paper so far, but I am not on FB which I despise for assorted reasons. In any case, as my paper as well as Longrich and Saitta's last year show, there are three actual juvenile Tyrannosaurus juveniles (Fig. 8B-D in my paper) that have the same number of teeth as the grownups. That is the normal reptilian pattern also observed in the other tyrannosaurid growth series. There is no example of a reptile losing teeth with growth (except when replacing dentition with a beak as per limusaurs, other beaked theropods have the beak and no teeth from the get-go). That the other small TT-zone eutyrannosaurs have more teeth (Fig. 8H-I and probably E) automatically excludes them from Tyrannosaurus because such variable tooth counts don't occur in reptiles including other theropods, a point Gilmore knew about eight decades ago. Why do so many current paleos Cau among them don't realize this here in the 2000s I have to wonder. Putting specimens with so many teeth into Tyranno violates parsimony big time and is so far outside the null paradigm. 

GSPaul

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[Tyler Holmes]

I haven't seen this mentioned yet in regards to tooth count, but Woodruff et al. 2018 on the cranial ontogeny of the Mother's Day Quarry Diplodocus specifically notes that the dentary tooth count decreases by two, from 13 down to 11. This in another saurischian dinosaur not going from teeth to a beak, so it might be more relevant than Limusaurus as an example. 

Refs:

Woodruff, D.C., Carr, T.D., Storrs, G.W., Waskow, K., Scannella, J.B., Nordén, K.K., and Wilson, J.P. 2018. The smallest diplodocid skull reveals cranial ontogeny and growth-related dietary changes in the largest dinosaurs. Scientific Reports, 8, 1:14341.
https://doi.org/10.1038/s41598-018-32620-x

TA Holmes

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[Skye McDavid]

MDQ Diplodocus putative decrease in tooth count is based on a single specimen, and a difference of 2 teeth is well within the range of individual variability. This is acknowledged by the authors of that paper. A couple years ago I looked into possible tooth count changes during ontogeny in Coelophysis, which has probably the best sample of any theropod (with the possible exception of a few Jehol paravians supposedly known from hundreds of specimens of which only a handful have been studied) and it would be easy to get the impression of tooth count changing one direction or another depending on which skulls you looked at, but looking at a larger sample size, there is high variability in tooth count but it is not correlated with ontogenetic age or maturity. 

High tooth count variability is consistent throughout ontogeny. 

https://doi.org/10.4202/app.01085.2023 

I'll let you make your own conclusions as to what that means for the proposed synonymy between Nanotyrannus and Tyrannosaurus.

Skye McDavid
(she/her)
https://www.skyemcdavid.com/
This message was sent at a time that is convenient for me. I do not expect you to reply outside of your normal working hours

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[Tim Williams]

'Gregory Paul' via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com> wrote:

> There is no example of a reptile losing teeth with growth (except when replacing dentition with a beak as per limusaurs, other beaked theropods have the
> beak and no teeth from the get-go).

From Wang et al. (2017) doi.org/10.1073/pnas.1708023114:

"Some specimens of _Sapeornis_ (STM 16–18 and STM 15–7) (23) possess a combination of two dentary teeth and three fossa-like alveolar homologs anterior to those teeth, whereas larger specimens have a toothless dentary (e.g., BMNH C-PH1067; SI Appendix, Table S2). The specimen LPM B00015 preserves no dentary teeth (SI Appendix, Fig. S1)..."

The SI contains other examples of ontogenetic edentulism (including possibly _Jeholornis_, but this is murky.)

[Franco Sancarlo]

Paul had already given an example and it seems to me that they have a beak

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[Gregory Paul]

Correct. So far no one has produced an actual example of a reptile that loses teeth as it grows in a consistent manner unless there is a shift during ontogeny from teeth to beak in some manner (limusaurs, some basal birds). This affirms what is very very probably true, that it just does not happen. 

Ergo the hypothesis that Tyrannosaurus did not experience an overall tooth loss while growing up is the parsimonious null hypothesis -- after all, the adults had among the longest jaws known in dinosaurs, why would they lose teeth! It follows that the burden has been and will be to show that for some reason Tyranno alone lost teeth as it matured. And that while juvenile Tyranno had a very variable tooth count from the same as the adults (which of course are the actual young Tyranno) to much higher, and the latter lost teeth, which never happens in reptiles. That is a deeply nonparsimonious conceit that is far from the null. The belief that requires extraordinary evidence for it to hope to be viable. 

And who first and correctly applied parsimony and the null hypothesis to the TT-zone tyrannosaurs using good, solid, tried and true comparative anatomy and ontogeny. Including that tooth counts don't decline in reptiles. And showed that the TT-zone was not just T. rex? EIGHTY YEARS AGO!

Why good old Charles W. Gilmore (who looks like he could be in a horror film;)! Who did not blink a paleo eye and put Nano into its own species. No muss, no fuss. He deserves major credit for correctly showing that the TT-zone contained multiple tyrannosaurs, the null hypothesis that has never been refuted with a sound analysis to the contrary. 

GSPaul 

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[Isaac Wilson]

I'd certainly consider the lack of apparent evidence of ontogenetic non-beak tooth loss in theropods one of the stronger pieces of support for Nano, especially after reading Napoli's preprint. I'm interested to see where else the discussion goes.

 2024.10.25.620216v1.full.pdf https://share.google/Dot4PoAVw5WLKgKGR

Isaac

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[Franco Sancarlo]

He says that Carr 1999 partially explains the loss of teeth. But we can notice ourselves that in the Gorgosaurus juvelinae ( RTMP 1991.036.0500 , AMNH 5664, RTMP 94.12.155 ) the number of teeth does not change and is even lower.

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[Gregory Paul]

I wonder if Carr 1999 was mislead by Bakker et al. 1988, which incorrectly states that AMNH 5664 has 15 maxillary teeth. Which is in Table 2 in Carr 1999. 

That Table 2 is critical. If not for the error of thinking that another tyrannosaurid lost teeth, and that then Tyranno could have also, then the everything is T. rex hypothesis might not have come into existence. Only if it could be shown that a tyrannosaur species did lose teeth would Gilmore's  multiple tyrannosaur taxa hypothesis not be the go-to parsimonious null hypothesis up to today. Unfortunately, even after the error was quickly exposed, the paleoestablishment went big time for the ETRH despite its flying in the face of what is known about amniote and reptile ontogeny. And the protests of Larson who showed that Jane had too many teeth and Bloody Mary and Jodi hands are too long to have reduced down to Tyrannosaurus hand size. While actual young Tyrannosaurus have the correct tooth count. 

And Tyrannosaurus growth being like teleost fish? Talk about violating parsimony in spades in an attempt to save a nonnull hypothesis. Gilmore who understood straightforward comparative anatomy and amniote ontogeny would be rolling his eyes at that one.  

Another example of Carr selectively using contents of a paper to errantly argue for ontogenetic tooth loss in reptiles is in the 2020 study in which he cites Brown et al. (2015) for that purpose, when the paper plainly concludes that such does not occur. 

I was not aware of the below preprint. Guess could not have cited it in the Mesozoic paper anyhow. 

GSPaul

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[Giggino Demente]

can you kindly explain the difference between the 2 techniques used thank you very much

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[Gregory Paul]

Not sure what the below request refers too. 

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[Jerry Harris]

I wonder if micro-CT or nano-CT scans of the dentigerous bones of the "lower tooth count" individuals might show newer, differently organized bone infilling places where sockets were in the toothier, hypothetically juvenile individuals. If so, it would be prima facie evidence that an individual used to have more teeth, but lost some and sealed up and filled in the former sockets during ontogeny.

[Gregory Paul]

Probably won't show old sockets because is so unlikely to have happened, and some adult maxilla don't have much room for them. But if done would probably be yet more evidence against the ETRH. 

GSPaul

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.

[Franco Sancarlo]

Wasn't CMNH 7541 an adult?

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[Jaime Headden]

> Maybe I’m missing something here, but if these Nanotyrannus/Stygivenator specimens were to undergo a rapid shift from sleek and long-legged to robust brutes, would it not stand to reason that the number of dentary teeth would stay the same throughout their ontogeny?

Not necessarily. Ontogenetic dental loss and even absorption does happen, simply because it's been uncontroversially accepted to do so in Limusaurus. Absorption of tooth positions (mostly germs, but in some taxa such as pangolins, more substantial teeth are absorbed) occurs perinatally in various mammals, and apparently also in some genetic studies on birds. So the assumption that it cannot happen in larger bodied animals is not tenable. But apart from that, the basic assumption is that animals do not undergo significant biomechanical and proportional changes from hatching to adult, which I find, as a human, rather odd to argue. 

Ontogenentic shifts in limb proportions, for instance, are well documented in various varanids and other scansorial to arboreal lizards, in which the toe length to leg length must vary to secure a grip, while dietary shifts also occur. (I'm willing to posit at this point that juvenile globidensin mosasaurs probably exhibit such a shift, with thicker, crushing teeth erupting as they switch from one soft-bodied diet in their youth to a harder one in their sub-adult to adulthood.) In tyrannosaurs, Tarbosaurus bataar ontogeny follows that of Gorgosaurus libratus except it undergoes a dramatic peramorphic shift: the adults become far more robust than their subadults. This is in contrast to the alioramin tyrannosaurines, which appear to undergo a paedomorphic retention of the juvenile state into adulthood.

Yet, for some reason, this doesn't happen to tooth positions? Because ... Nanotyrannus?

Putting aside the entire issue, we've observed not just substantive but demonstrative gracile-to-robust ontogenetic shifts in related dinosaurs (Gorgosaurus) without any argument as to whether the juveniles so found are different taxa, although that was the case with various taxa now considered mostly "Tarbosaurus" bataar---for which there are a plethora of gracile, shallow-snouted, long-legged juveniles and subadults with their own monickers. Even if Raptorex is not a juvenile Tarbosaurus, it's still a juvenile and the basic proportions extend to Shanshanosaurus and Maleevosaurus, etc.

Without a doubt, ontogenetic transformation occurs, and can include tooth loss. It's important to note that we should expect this to show up in the fossil record: it doesn't just happen as a function of turning genes on and off: there would be individuals in a population with fewer teeth than others. The tooth count must, by nature, vary when not under constraint. (Especially in humans, with failure of third lower molars to erupt, due perhaps to mandibular shortening possibly coinciding with humans adapting to eating a less coarse, tough diet, resulting in a shorter jaw.) This is especially important considering that we've not questioned when it happens in Limusaurus, but seem up in vapors when it comes to tyrannosaurs, because suddenly Nanotyrannus---? 

It's simple: To prove the counterfactual, find a juvenile Tyrannosaurus among the growing number of non-adult tyrannosaurin latest Cretaceous North American specimens that has the T. rex tooth count and whatever other features one must be assuming has to be present in the juvenile/sub-adult, but not, magically, the adult. This was the question posed to the Triceratops/Torosaurus debate, and what do you know: Mallon et al (https://academic.oup.com/zoolinnean/article/195/1/157/6540273?login=false) argue just such a case: a Torosaurus-like frill from an osteologically immature individual.

It behooves the principle debaters to look for this data, instead of trying to "prove" Nanotyrannus, because at this point, it's becoming a litmus test for how serious one might take research when they disagree with its results. As for the rest of us, myself included, it's best we hold on to the actual data that's been presented and stop trying to "both sides" this issue. Greg brought up the Null Hypothesis, and it behooves everyone to study the logic that must underlie one's arguments when using the term:

The null, as it were, presents the baseline assumption from which the argument then derives. There is no one specific null here: the null for ontogenetic tooth loss is that it exists; although possibly not in this lineage. Parsimony argues that should we constrain everything to the same measure of expectation, then tooth loss is an exceptional argument, which it is; but then that to propose it for a given set of specimens from which an ontogenetic series is composed, one must back it up with substantive evidence or a lack of contravening evidence. And we have a wealth of both.

This will not be solved, to many Nano proponents, until a juvenile T. rex, robust, incrassate, and glorious in tiny tyranny, is found with fewer dental positions (and I suppose a lack of all those "albertosaurine" features that led many of such people to argue that Nano was, in fact, an albertosaurine).

Until then, tyrannosaur ontogeny is, at this point, well-documented: They had proportionately longer arms, shorter torsos, bigger heads on longer necks, and much, MUCH longer legs. A variety of other features relate to attaining massively large size as they grew from greyhound to ostrich to rhino to elephant to ... much larger size. Nano looks like what a subadult Tyrannosaurus rex should look like, when compared to Albertosaurus and Tarbosaurus. Unless those animals, like Athena, sprung whole from the head of their parent, adult in their own tiny tyranny.

Cheers,

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[Milo Gaillard]

I’m not taking a side in this debate right now. However, I will show you this. It makes a pretty compelling case in favor of Nanotyrannus being valid. Just read it with an open mind.  https://www.biorxiv.org/content/10.1101/2024.10.25.620216v1.full.pdf

Thank you for your time.

-Milo Gaillard

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[Franco Sancarlo]

I think all the issues brought up are addressed in Paul (2025), plus you forget that Jane is almost an adult, the holotype is perhaps an adult. as Paul said before the number of teeth does not decrease in beakless reptiles, if you say that Tyrannosaurus has a high beak then you could be right, if as already shown in Paul 2025 their mass gain does not coincide with Tyrannosaurus

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[Franco Sancarlo]

This paper has been addressed before, Carr 1999 says that in Gorgosaurus the number of teeth decreases with growth (point that in the paper says that the number of extra teeth is justifiable) the problem is EVERY young Gorgosaurus specimen we have shows that it has either the same number of teeth or a lower number (RTMP 1991.036. 0500, AMNH 5664, RTMP 94.12. 155)

[Gregory Paul]

JH is just plain wrong in so many ways. He shows no familiarity with the literature or even the ongoing discussion on the list. He is engaging in idle blowharding. 

As shown by Larson over the years, Burnham et al. in the SVP 2018 abstracts, Longrich & Saitta last year, and me this year, there are a number of actual juvenile Tyrannosaurs specimens that have the same low, low tooth count as adult Tyrannosaurus (se my Fig. 8A-D). The other small TT-zone tyrannosaurs of the same size have more teeth (Fig. 8G-I and probably E), and there is to date no know example of a reptile extinct or extant that loses teeth with ontogeny as shown in a many many papers (not yet contradicted by anyone on the list) if they are not switching from dentition to a beak. 

Who says that ontogeny does not often involve allometric changes in limb proportions? What does that have to do with tooth counts? 

Let us leave the blow harding to those web comments sections. If discussing items that have been published in the peer reviewed literature please be familiar with the pertinent data.

Thank you, 

GSPaul 

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[Gregory Paul]

The errant Gorgo ontogenetic tooth count loss with maturity in Table 2 by Carr 1999 JVP was quickly refuted, I think first by Currie 2003. The big question is why after the proof that tryannosaurids, Tarbo included, do not lose teeth, why the notion that Tyranno did has continued. It is as non a null hypothesis as you can get.  

GSPaul

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.

[Jaime Headden]

The argument that the dinosaur has to develop a beak to demonstrate this is problematic, because there's only one example of a taxon in which teeth are fully erupted and present and reduced during ontogeny: Limusaurus. This doesn't happen in birds. What happens instead is that tooth germs (which begin forming enamel and dentine, but remain inside the jaw bone and do not even absorb bone material in order to "erupt"--creating alveolar bone to support them) are absorbed directly or their development is stalled, and bone remodelling in ontogeny destroys those remnants. This supposedly happens in sloths, pangolins, frogs, likely mysticete whales, and would happen regardless if the origin bone bore a beak or not (unless someone wants to tell me pangolins and frogs have beaks). Thus it is disingenuous to claim it happens in "beaked" animals, since no fossil bird taxon shows this condition---unless you count variability in tooth expression as possibly being ontogenetic, for which so far there doesn't seem a detailed analysis considering.

And if it did happen in beaked animals, it would happen because of the effective growth of a beak and should happen in more than just Limusaurus, but for which we lack data regarding other taxa---but this makes it a testable hypothesis. For instance, it was once implied to be the case for caenagnathid oviraptorosaurs that socket-like features of the mandibular bones represented nascent tooth positions that were later lost in oviraptorids. It is Greg Funston's general argument, borrowed from pavement first laid by Phil Currie in the 1990s, that these features are novel structures and not fundamentally nascent or atavistic tooth sockets. Largely because in turtles, similar features appear and have nothing to do with teeth. Similar features in some mysticete whales have been likened to atavistic tooth sockets, but they devoid of alveolar bone, which strains their identification.

I find it odd to tout Limusaurus as being so exceptional that, among all possible animals that it could have occurred in, only it and it alone ever expressed this ontogenetic tooth loss, and that it, by nature, coincides with a developed beak. One point of that is a stretch.

Alternatively, ontogenetic tooth loss in support of the growth of a beak would develop in such a way as to advantage the mechanic support that a beak provides, which is generally to reduce strain, and occurs when the bone already fuses to its neighbors to do the same, and while beaks are generally found on the dentary (with a fused symphysis), premaxillae (same), and maxillae (when fused to the premaxillae), then onto the nasals (see previous two bones). These only co-occur: beaks grow along with or after underlying bone fusion (and it's thus possible Limusaurus lacks a substantive beak; which is the stretch I mentioned above). 

Cheers,

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[Franco Sancarlo]

well you have given many examples, but answer this question. do you have evidence that it happens in dinosaurs that are not Limusaurus or birds. Limusaurus completely changes its diet from carnivore to herbivore, tyrannosaurus has no reason to lose extra teeth both Jane and the holotype are too mature to have such a drastic change. read Paul (2025) before speaking please, it is literally free access

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[Gregory Paul]

Someone I think today posted a reference to a Mesozoic bird that had teeth as a juvenile lost as the beak developed. That may have been fairly common in basal birds. 

Otherwise, what the below has to do with the proposed loss of teeth in Tyrannosaurus which has lips (as per by in-depth analysis in Prehistoric Times a few years ago, and Cullen et al. in Nature a couple years of ago which cites my PT article) not a beak and a row of big teeth, I do not know. 

GSPaul

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[The Dinosaur Heretic]

With this in mind, would Limusaurus’ loss of teeth throughout its ontogeny at all correlate to ontogenetic niche partitioning? If so, would this trend be applicable to Tyrannosaurus as well? In other words, why would juvenile Tyrannosaurus bear more teeth than adults?

I’m by no means suggesting this validates Nanotyrannus, only that Tyrannosaurus had a consistent number of teeth throughout their growth, and that an adult T. rex with 16 dentary teeth probably did exist (at least based on the maximum number of dentary teeth in CMNH 7541). I’m aware that without any fossil evidence, this is but a silly hypothetical.

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[Jaime Headden]

The evidence it happens in Limusaurus is based on general morphology of a bonebed association of multiple age groups, most of them juveniles (in fact, the sample specimens with teeth are generally all half the size of the adults---there are no intervening size classes). Some juveniles show intermittent alveolar loss, while also showing osteologically immature bone in their tibiae and gastralia. Adults lack any sort of teeth save for remnant alveolar sockets and a mandibular alveolar canal (they lost all sockets and thus alveolar bone). The specimens in question have radically different jaw shapes and proportions between the two sizes. If one found only the juveniles or only the adults, they would be harder pressed to assume they were the same taxon. As is usually typical with taxa, juveniles make poor taxonomic exemplars. This taken together is not substantive, but it's generally unrefuted because people didn't balk at "ontogenetic tooth loss" as a process.

All things being equal, it makes sense they're the same taxon; they co-occur; there are discrete ontogenetic markers to indicate some are younger than the others; tooth loss is intermittent (from the middle of the jaw, not the ends); thus, ontogenetic tooth loss occurred. However, tooth loss in adulthood is absolute, it's not from the ends. It would be in taxonomic progression towards mechanical reasons to reduce tooth count (for example, just tossing this out there, increased muscle attachment area relative to tooth row size). As in humans (and this is also something that just baffles me why I have to bring it up) tooth loss can lead to alveolar closure: alveolar bone remodeling and closure can occur as a response to trauma and tooth removal even in adults. It would be ludicrous to assume it doesn't happen in other taxa. Like ... tyrannosaurs.

Cheers,

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[Gregory Paul]

There is not a single example of a tyrannosaur species losing teeth with growth. None. 

I kinda think JH is pulling our legs here. 

GSPaul

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[The Dinosaur Heretic]

I don’t necessarily think so. Jaime’s information is very insightful. I just don’t think I’m posing my questions correctly lol

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[Gregory Paul]

A problem with this is that the other giant tyrannosaurid species underwent major dietary changes from being cute adorable little bug and lizard eating nestlings to ceratopsid and hadrosaur killers, and did not lose teeth. Same with all large reptiles which never lose teeth. A few gain them, some a whole lot, but no losses. To suggest that Tyrannosaurus along out of Reptilia did so is deeply nonparsimonious, and wrong because the actual juveniles have the same # of teeth as their parents, like the other tyrannosaurids. 

Also, people keep going on and on and on and on and on and on about Nanotyrannus. That is just one skull, and is the only fossil that the name can be applied to with confidence. As hinted at in Longrich and Saitta, and as I discuss at lengthl, Jane, Petey, and especially Bloody Mary and Stygi are not the same taxon as the Nano holotype which does not look like the rest of them. We should be saying baso-eutyrannosaurs, since they are most if not all not tyrannosaurids. 

GSPaul

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[Tim Williams]

Gregory Paul' via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com> wrote:

> There is not a single example of a tyrannosaur species losing teeth with growth. None.

Circular reasoning here, because you do not regard CMNH 7541 (_Nanotyrannus_) as a juvenile _Tyrannosaurus_.  

To clarify, I'm not definitively saying that _Nanotyrannus_ is a juvenile.  But, as I stated previously, and alongside Jaime's _Limusaurus_-based insights, the latter taxon demonstrates that extreme ontogenetic change can occur in theropods.  IMHO the exact transformation in _Limusaurus_ (toothed jaws replaced with a toothless beak) is less important than it shows that profound morphological change can occur within ontogeny.  If we didn't have a growth series for _Limusaurus_, would we have inferred that juvenile and adult specimens of this ceratosaur actually belonged to the same species?  

Personally, I think it would be great to have multiple tyrannosaur genera in the "TT-zone", and I'm open to the idea that _Nanotyrannus_ and/or _Stygivenator_ might be valid.  But some of the arguments raised against the so-called "everything is Tyrannosaurus rex hypothesis (ETRH)" are very hand-wavey and rhetorical - such as the (alleged) inherent implausibility of the required ontogenetic changes (including reduced tooth count).

Finally, I'll reiterate one observation made by Voris et al. (2025): "However, noteworthy evidence, discovered in the context of this research, of a tooth count reduction in _Tyrannosaurus_ is present in the CT scans of the adult specimen FMNH PR 2081 where a resorbed 13th alveolus is present at the posterior end of the left maxillary tooth row. This structure is completely enclosed by bone ventrally (such that no tooth could have erupted), but nonetheless appears to be the 13th alveolus. As far as we are aware, this would exceed the maxillary tooth count values known for adult _Tyrannosaurus_ and would provide evidence that tooth counts can reduce through ontogeny in this taxon."

[The Dinosaur Heretic]

That snippet from Voris et al., 2025 is totally novel to me. Very interesting stuff. Much appreciated Tim!

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[Franco Sancarlo]

 it seems to me that as said in Paul (2025) Nanotyrannus has been proven to be adult or at least close to adulthood, same goes for Jane. In addition it would be necessary to observe whether this absorbed alveolus is also present in young individuals who have the same number of teeth and if there is it would be an evolutionary remnant

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[Jura]

Can we get the full citation for this? Voris has two senior-authored papers from this year (that I've seen) and I can't find this sentence in either one.

Thanks,

Jason 

[Tim Williams]

The Dinosaur Heretic <thedinosa...@gmail.com> wrote:

> That snippet from Voris et al., 2025 is totally novel to me. Very interesting stuff. Much appreciated Tim!

No problem!  This is from the Supplementary Information of Voris et al. (2025) doi.org/10.1038/s41586-025-08964-6   There's a lot of interesting stuff here.  Quite a few tyrannosaur species are sent to Coventry.

[Jura]

Ah, of course it was in the supplement. I should expect nothing less from a Nature paper. :)

[Franco Sancarlo]

Tim no offense, but the data reported as written is present only on the left maxilla, Sue also has the right one. In addition it is a single specimen the data could be potentially pathological since as written there "but nonetheless appears to be the 13th alveolus" they do not have the certainty that it is an alveolus. In addition it would be necessary to see if this structure is also present in the other specimens, if not present it could have been a coincidence, keep in mind that Sue has serious signs of distortion. Using this single data as proof of the decrease in Tyrannosaurus teeth makes no sense until future tests

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[Tim Williams]

I totally agree - more work is needed.  

And no offense taken.

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[Gregory Paul]

I addressed the new Voris et al observation at the last minute in the Supplementary. The loss of one tooth in a maxilla of an adult does not show that ontogenetic tooth loss occurred in Tyrannosaurus, when the actual juveniles of the genus have the same low tooth counts as the adults, and tooth loss does not occur in nonbeaked reptiles. 

GSPaul 

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[Gregory Paul]

It is not even close to circular reasoning. We already have three actual juvenile Tyrannosaurus with the same tooth counts as the adults, and there is not a single known documented example of a nonbeaked reptile species losing teeth. It is for no actual reason speculating that Nano, Petey, Jane and prob Bloody Mary for some weird reason lost teeth while undergoing sudden ontogenetic changes via fish like metamorphosis never seen in amniotes which a basic characteristic of which is they do not experience metamorphosis that dumps straightforward parsimony into the trash. It is part of the cultish obsession that Tyrannosaurus is just so special that it did what no other amniote does. It was just another dinosaur. 

GSPaul

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[Adam Yates]

The statement that no reptile loses teeth through ontogeny, unless they are being replaced by a beak is not quite true. Extant Crocodylus species almost always go from five premaxillary teeth at hatching to four teeth in adults. It is the second tooth that is lost, usually in late stage juveniles. Whether this is relevant to the loss of multiple tooth positions or not, I'll leave up to you guys.

see:

Brown CM, VanBuren CS, Larson DW, Brink KS, Campione NE, Vavrek MJ, Evans DC. Tooth counts through growth in diapsid reptiles: implications for interpreting individual and size-related variation in the fossil record. J Anat. 2015 Apr;226(4):322-33. doi: 10.1111/joa.12280. Epub 2015 Feb 16. PMID: 25689039; PMCID: PMC4386932. 

[John D'Angelo]

Tyler Holmes said:

> I haven't seen this mentioned yet in regards to tooth count, but Woodruff et al. 2018 on the cranial ontogeny of the Mother's Day Quarry Diplodocus specifically notes that the dentary tooth count decreases by two, from 13 down to 11. This in another saurischian dinosaur not going from teeth to a beak, so it might be more relevant than Limusaurus as an example.

Skye already responded to this, but I'd like to add that the skulls discussed by Woodruff et al. do not belong to the same species and probably do not belong to the same genus. CM 11161 (adult with 11 dentary teeth) probably belongs to one of the two diplodocine species known from the Carnegie Quarry, Barosaurus lentus or Diplodocus hallorum. Contrary to what Woodruff et al. 2018 state, the dentary tooth count is not known in CM 11255 (Whitlock et al. 2010). CMC VP 14128 (juvenile with 13 dentary teeth) probably does not belong to either B. lentus or D. hallorum, as neither species appears to be present at the Mother's Day Quarry; I'm not convinced the "Mother's Day Diplodocus" is even Diplodocus. So there's currently no evidence for an ontogenetic decrease in tooth counts in diplodocids.

Gregory Paul said:

> There is no example of a reptile losing teeth with growth

This is far from a comprehensive survey of the literature, but an apparent decrease in tooth count through ontogeny has been reported in Opisthodontosaurus carrollii (Haridy et al. 2018) and Stenopterygius quadriscissus (Dick and Maxwell, 2015), as well as occurring in the premaxilla of Crocodylus porosus as a consequence of interference from the first dentary tooth (Brown et al. 2015). Outside of Sauropsida, the loss of tooth positions through ontogeny can also occur in synapsids, such as Brasilodon quadrangularis (Cabreira et al. 2022) and Orycteropus afer (Davit-Béal et al. 2009). Ontogenetic decreases in tooth counts are rare, but they do happen, and for a variety of different reasons. Perhaps none of these situations is exactly analogous to what has been hypothesized for T. rex, but none of them are exactly analogous to each other either.

- Brown, C. M., VanBuren, C. S., Larson, D. W., Brink, K. S., Campione, N. E., Vavrek, M. J., & Evans, D. C. (2015). Tooth counts through growth in diapsid reptiles: Implications for interpreting individual and size‐related variation in the fossil record. Journal of Anatomy 226(4), 322–333. doi: 10.1111/joa.12280

- Cabreira, S. F., Schultz, C. L., da Silva, L. R., Lora, L. H. P., Pakulski, C., do Rêgo, R. C. B., Soares, M. B., Smith, M. M., & Richter, M. (2022). Diphyodont tooth replacement of Brasilodon—A Late Triassic eucynodont that challenges the time of origin of mammals. Journal of Anatomy doi: 10.1111/joa.13756

- Davit‐Béal, T., Tucker, A. S., & Sire, J. (2009). Loss of teeth and enamel in tetrapods: Fossil record, genetic data and morphological adaptations. Journal of Anatomy, 214(4), 477–501. https://doi.org/10.1111/j.1469-7580.2009.01060.x

- Dick, D. G., & Maxwell, E. E. (2015). Ontogenetic Tooth Reduction in Stenopterygius quadriscissus (Reptilia: Ichthyosauria): Negative Allometry, Changes in Growth Rate, and Early Senescence of the Dental Lamina. PLOS ONE 10(11), e0141904. doi: 10.1371/journal.pone.0141904

- Haridy, Y., LeBlanc, A. R. H., & Reisz, R. R. (2018). The Permian reptile Opisthodontosaurus carrolli: A model for acrodont tooth replacement and dental ontogeny. Journal of Anatomy 232 (3), 371–382. doi: 10.1111/joa.12754

- Whitlock, J. A., Wilson, J. A., & Lamanna, M. C. (2010). Description of a nearly complete juvenile skull of Diplodocus (Sauropoda: Diplodocoidea) from the Late Jurassic of North America. Journal of Vertebrate Paleontology, 30(2), 442–457. doi: 10.1080/02724631003617647

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[Milo Gaillard]

This actually makes a good case for archosaurs having no evidence of losing their teeth throughout growth (link: https://www.biorxiv.org/content/10.1101/2024.10.25.620216v1.full.pdf)

-Milo Gaillard

Sent from my iPhone

On Jul 3, 2025, at 19:44, The Dinosaur Heretic <thedinosa...@gmail.com> wrote:



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[Jaime Headden]

>  It is as non a null hypothesis as you can get.  

All things being equal, if this is the hang-up upon which Nano is debated, then it becomes irrelevant to the taxonomic debate. But of course, it's not; and never has been. The debate had depended upon the moving of goal posts, but this is the one that the Nano-argument keeps returning to, so it must be the point that must be contended. If it's the sole issue that keeps us here---then it needs to be shown why it, and it alone, is sufficiently informative taxonomically.

Cheers,

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[Russell Engelman]

> Outside of Sauropsida, the loss of tooth positions through ontogeny can also occur in synapsids, such as Brasilodon quadrangularis (Cabreira et al. 2022) and Orycteropus afer (Davit-Béal et al. 2009).

I realize this is in mammal world and not dinosaurs, but I've straight up observed that about 20-30% of all Eira Barbara specimens in museum collections will lack m2 as part of natural individual variation. Most of these are from the same Central American populations so it's unlikely there are cryptic species present.

The reason I bring this up is m2 is Eira is not vestigial but is actually fairly large and functional. So if in mammals, in which molar tooth count is normally highly conserved, you can straight up lose a functional molar in a minority of the population, it suggests tooth count variation in sauropsids (where obviously precise occlusion is much less of a concern), it really makes you wonder if individual variation in tooth count might be more of a thing.

In particular, Skye's comments about individual variation in tooth count in Coelophysis sounds very interesting. I wonder how that also applies to Allosaurus, which I would assume would be the other toothed theropod for which we could get good sample sizes across a broad ontogenetic spectrum.

[Jacqueline Silviria]

M3/m3 loss is also common in modern humans and, surprisingly, Denisovans.

Guillermo Rougier pointed out to me a while ago that the bulk of evo-devo literature on heterodont mammalian odontogenesis supported the notion of teeth being lost or gained at the ends of modules rather than within them. For example, assuming incisors, premolars (p1-5) and molars (m1-3) are separate “fields” of “clones” (reconciling the Butler and Osborn models of tooth germ development sensu Mitsiadis & Smith and Townsend et al.), you are more likely to lose p1, p5, m1, or m3, or gain a p6 or m4, than have any other possible gain or loss, with losses being relatively more common than gains. This is why the loss of the P3/p3 locus in therians (metatherians+eutherians) pointed out by Osborn, Schwartz, McKenna, Novacek, O’Leary et al. is so weird and was so fiercely denied by Luckett, since it’s smack in the middle of the premolar module. Yet it's a developmental novelty well-supported by both genetics and fossils (albeit opening the uncomfortable possibility that certain five-premolared "basal eutherians” like Zhelestidae, Otlestidae, Juramaia, Eomaia, Maelestes, a lot of specimens in the “Batodon” and “Gypsonictops” dumping grounds, etc. are actually be stem-therians, which has been subtly alluded to by Thomas Martin, but I think needs to be taken more seriously given the lack of developmental synapomorphies for Eutheria as traditionally recognized). Odontocete cetaceans obviously got lots of supernumerary teeth when they changed from heterodont or homodont, because constraints on tooth germ development and differentiation were lost as the incisor clonal field expanded distally. I’m curious if anyone knows whether the cetacean development pattern is considered a reversal to what is seen in earlier synapsids as well as most sauropsids.

This leads to something I think is left out in the Nano (non-)debate: observed generality does not guarantee universality (there is a reason linguists distinguish between “absolute” and “statistical universals). If the general/plesiomorphic condition in theropods and archosaurs more broadly is constancy in maxillary tooth count through ontogeny within a population, due to ultraconserved gene-regulatory pathways (which, given Skye’s remarks on Coelophysis, may not be remotely true, and that is interesting in it of itself because it means this entire talking point is moot in arguments over alpha taxonomy), does that completely negate the possibility that Tyrannosaurus rex had reduction in tooth count due to alveolar reabsorption? I would argue no, it does not it. Unexpected developmental anomalies like that very rare but they do happen; see also the above example with P3/p3 loss in Therian. I agree with Jaime this is a weird thing to get hung up on.

Jacqueline S. Silviria

she/her/hers

The Last King of the Jungle

Department of Earth & Space Science
University of Washington
Seattle, WA, USA
jsi...@uw.edu, sympan...@gmail.com

ResearchGate profile

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[Aiden Younk]

It never ceases to amaze me how the goal post gets moved so constantly, as mentioned in another post.

'There's no examples of tooth loss in other taxa' was the original hangup. While homology certainly bolsters confidence, if the data shows tooth loss and it resolves as a growth character and not individual variation, then that's what we accept. Not to mention the other synontomorphies that support the growth assignment. Now people are finding exemplars among taxa that aren't _Limusaurus_, which as we all know by now isn't comparable.

Insert Voris et al. (2025) here, another exemplar but more closely related. CT scans of FMNH PR 2081 show a resorbed alveolus that is closed off, and now the doubt is 'well maybe it's pathological'. Pathologic bone tissue looks different than normal tissue, and shoudn't be something that can't be checked. While it's certainly a possibility, it needs to be investigated.

In ontogenetics, we adhere to a variant of Hennig's Auxillary Principle, called the Ontogenetic Auxillary Principle, which states that we assume characters are growth related when lacking contrary evidence, and the sealing of an alveolus (possibly due to increased tooth size pushing a tooth out and the growth-related sealing of an alveolus) is an explanation for tooth loss. 

Greg claims Carr (2020) is selective with Brown et al. (2015), and now that other taxa have been brought in to question tooth loss they're wrong and it doesn't count and something is different? 

I'd love to see an ontogram or a cladogram in a Greg paper to demonstrate everything is as he says. If an ontogram of all _Tyrannosaurus_ resolves cleanly and there's no tree that offshoots to support your claim of new species, and tooth count resolves as a reversal near the periphery of the tree, then what? Alternatively, a cladogram with T. rex, T. regina, T. imperator, and Nanotyrannus in a polytomy.

More data is needed (CT scans, subadult dentition data as noted by Carr (2022), specimens) to know for sure. 

The goal post will forever be moved forward.

Aiden Younk

Carthage College '26

Biology Major // Geoscience Minor

Paleontology Track

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[Christophe Hendrickx]

Well, I actually recently compiled information on tooth count in non-avian theropods for a project on their dental evolution. I made an Excel sheet showing the difference in tooth count for each genus-level taxon and this is what I compiled for the taxa that have more than one tooth of difference in the maxilla and dentary:

- Coelophysis: mx 13 to 28 (difference of 15 teeth!); dt 17 to 27 (diff of 10 teeth!). Data from Buckley and Currie (2014). That's an enormous difference in tooth count in the maxilla and dentary in Coelophysis, one of the best sampled dentulous theropods out there.

- Megapnosaurus rhodesiensis: mx 19 to 22 (3); dt?

- Ceratosaurus: mx 12-15 (3); dt 11 to 15 (4).

- Juvenile Limusaurus: mx 5 to 8 (3); dt 11 to 12 (1)

- Torvosaurus: mx 10 to 13 (3); dt 13 to 13 (0). But there will be new information on the maxillary tooth count coming soon.

- Allosaurus: 15 to 17 (2); dt 15 to 17 (2).

- Albertosaurus: 12 to 15 (3); dt 15 to 15 (0). Carr. pers. comm.

- Daspletosaurus: 14 to 17 (3); dt 16? to 17 (1?). Carr pers. comm.

- Tyrannosaurus: 11 to 16 (5); dt 12 to 17 (5). Carr. pers. comm. This includes Nanotyrannus as Tyrannosaurus juvenile.

- Anchiornis: mx 12 to 14 (2); dt 16 to 16 (0).

As for the premaxilla, there is only one tooth of difference in Sinosaurus, Baryonyx (between the left and right pmx of the holotype), and Daspletosaurus.

You will quickly understand that those are the few nonavian theropods for which we have a good sample. Most of the others are only known from one or two specimens. So tooth count appears to fluctuate quite a lot in at least some theropod "genera" (for what it means). Now, some of them like Allosaurus, Megapnosaurus, and possibly Tyrannosaurus appear to include several species, so that's something to take into consideration. Likewise, I have not collected ontogenetic information about the specimens and cannot have an opinion on that. As far as I remember, juvenile Coelophysis had more teeth than the adult ones but I might be mistaken.

Regards,

C.

______________________

Christophe Hendrickx, Profesor Adjunto

Dinosauria Lab, Fundación Miguel Lillo &

CONICET-Unidad Ejecutora Lillo,

Museo Miguel Lillo De Ciencias Naturales,

San Miguel de Tucumán, Tucumán, Argentina

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[Franco Sancarlo]

I think you are referring to my comment on the pathological part of FMNH PR 2081. I also mentioned the fact that on the right maxilla this resorption is absent. In this case the Ontogenetic Auxillary Principle cannot be applied since in addition to the teeth Paul (2025) has highlighted other problems with including Nanotyrannus in Tyrannosaurus.

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[The Dinosaur Heretic]

Well that’s not necessarily always the case. We know of bilateral asymmetry in some dinosaur specimens, most notably in centrosaurines (UALVP55900, Lokiceratops rangiformis, a number of Pachyrhinosaurus lakustai specimens, and so on). Asymmetrical tooth rows in dinosaurs doesn’t seem unreasonable. I vaguely remember hearing about asymmetrical tooth rows in a tyrannosaur (Gorgosaurus or Daspletosaurus? I can’t remember).

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[Franco Sancarlo]

I would like to apologize if I expressed myself badly, I'm not saying that it doesn't happen, what I mean is that based on the evidence we have from Sue the decrease is present only on the left maxilla, on the dentary and on the right maxilla it doesn't happen for this reason to see if it's just a coincidence I proposed to see that in other specimens of tyrannosaurus a similar structure is present

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[Aiden Younk]

Besides the symmetry, if there is a problem with _Nanotyrannus_ being included in _T. rex_, Greg should have no problem showing it in an analysis. The fact that it resolves where it does in the growth series while also not being a wildcard that bounces around is strong evidence. The _Nanotyrannus_ specimens should resolve differently in the growth series if they are a different species. Until Greg can walk the walk rather than talk the talk, I and many others will remain skeptical. 

And you're right, not having both maxillae is frustrating and causes some issues since comparisons aren't congruent, nor is a single exemplar ample evidence of a pattern. It does, however, signify that the answer may be before us. At this point, CT scans of other specimens (adults exemplifying tooth loss) are needed to test this dichotomy. As stated before by Holtz, having private specimens doesn't help either, as some missing data could be filled and the growth series for T. rex could be more complete, although it is already high resolution regardless. For non-members of the SVP, it's a non-issue.

With T. rex in particular, there isn't a choice but to discuss private specimens that are known in the literature, since not including them has lead to baseless accusations (SVP 2024).

Aiden Younk

Carthage College '26

Biology Major // Geoscience Minor

Paleontology Track

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[Franco Sancarlo]

If I'm not mistaken Greg in the study shows that indeed Nanotyrannus was almost an adult and that even if it had not been it would have reached a weight of less than a ton. Jane has been shown to be almost an adult as well (Paul 2025, Longrich and Saitta 2024)

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[Aiden Younk]

At this point, I'll wait for the rest of the Tyrannosaurus crowd to publish a response and dissect every argument or some new evidence by Paul, Saitta, and Longrich that is undeniable proof that T. rex should be split and _Nanotyrannus_ is valid 

So far, its been a back and forth, and it will continue to be until incontrovertible evidence is brought forth. 

There are statements in Paul (2025) that just don't sway me, because he says there's a problem and refuses to elaborate, such as 'Carr et al.'s (2022) diagnosing Tarbosaurus bataar and Tyrannosaurus rex at the genus rather than the specific level produced unreliable results.' He never expands on this. What is the inconsistency or the nature of it? Is this an inconsistency others have found or just his cohort?

And this statement in Paul (2025). 'Characters used are only those this researcher is reasonably confident of being both accurate and applicable to the questions at hand.' This is the biggest problem for me personally. By this logic, Greg et al. can pick and choose characters they deem confident, which could shape the results they want. It is perfectly fine to not include characters there is hesitance in, but there needs to be a basis. The Materials and Methods should indicate what characters are disregarded, what publication provided that character, and the basis for disregarding. 

Not to mention the previous statements of Paul's taxonomic opinions. He's talked alot about parsimony, but fails to recognize that his current and previous propositions of splitting taxa do not adhere to the Principle of Parsimony. It isn't always true, and it's likely our general knowledge is simplified. 

Paul, Saitta, and Longrich could be totally right. The issue of Paul's previous taxonomic opinions with no basis and no provided taxonomy point to this being a similar case.

Aiden Younk

Carthage College '26

Biology Major // Geoscience Minor

Paleontology Track

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[Franco Sancarlo]

ok, do you have any criticisms of the paper itself besides these statements? because you know to be scientific you should criticize the paper, its methods and you should bring evidence to the contrary not hoping for a debunk. because I say taking 2 single sentences in 54 pages does not make much sense

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[Tim Williams]

Franco Sancarlo <franco.sa...@gmail.com> wrote:

> ok, do you have any criticisms of the paper itself besides these statements? because you know to be scientific you should criticize the paper, 

> its methods and you should bring evidence to the contrary not hoping for a debunk. because I say taking 2 single sentences in 54 pages does

> not make much sense

Aiden does raise a valid question about the methods by highlighting this sentence from Paul (2025). "Characters used are only those this researcher is reasonably confident of being both accurate and applicable to the questions at hand."  I also have a major problem with this approach to character selection; it casts a shadow over the entire paper.  

[The Dinosaur Heretic]

Putting it bluntly, it’s essentially “if it confirms my preconceived notions, then it must be valid.” Sorta the antithesis of the scientific method, no?

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[Stephen Poropat]

Several sauropod individuals out there with different tooth counts on either side of their jaws, off the top of my head Sarmientosaurus and one exemplar of Giraffatitan. Would be interesting to see how variable tooth count is under the Camarasaurus umbrella; pretty sure Madsen et al. (1995) give a range of values.

Also related to Adam Yates’ point about crocodiles: sauropods, as far as I am aware, universally have four premaxillary teeth. But one embryo, described by Kundrat et al., was described as having five. Looking at their image of the element in question, I could see a case being made for either four or five (and mention this in the Macronaria chapter of Dinosauria III); IIRC no internal scan data of the element was presented.

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/

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[Gregory Paul]

I am skeptical of the lower counts in Ceolophysis, especially those loooong nosed adults. I would want to see photographs of adult skulls with fewer teeth than juveniles. Colbert says the tooth count rose which makes sense and sometimes happens in reptiles, but that monograph is sometimes iffy (I visited retired Ned in Flsgstaff when he was doing that tome. He introduced me to the museum creator Ned Danson, who of course was the father of Ted Danson of Cheers, Curb Your Enthusiasm etc. fame, but I digress). Looking at the Buckley & Currie paper which does not claim tooth loss with maturity, I can't sort out the tables, and I wonder if some of the very low count tooth rows counted are incomplete due to breakage and/or coverage and the like. 

I don't think there are different tooth counts in the three Tyrannosaurus species, but I could be wrong. 

GSPaul

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[Gregory Paul]

In the paper I am referring to members of the Reptilia not losing teeth with growth. The synapsids are an entirely different clade that do a lot of wild things with teeth and are not a good model for a diapsid tyrannosaurid with standard reptilian dental maturation. 

I know some about the ichthyosaurs having done the sea reptile guide. Some of the tuna shaped examples' juveniles have massive numbers of very wee teeth that they further reduce in size and number so much so that when adult they are in practical terms toothless. This is sort of like the loss of teeth associated with beaks in some animals. Not comparable to the always massive toothed tyrannosaurs. 

Opisthodontosaurus is a very basal small reptile with hollow teeth sitting atop the jaw rim and have no sockets. 

There is still no example of a reptile that loses teeth with growth that comes anywhere near the situation in beakless, nonmarine, solid and big toothed Tyrannosaurus. 

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[Aiden Younk]

Sure, you can argue I'm nitpicking because I picked two sentences. I think they are big deals and, as Tim Williams agreed, cast shadows over the rest of the paper. When methodology isn't clear, how can it be replicable? Not that there's an analysis or anything. There's other phrases and verbiage I have issues with, but that is truly nitpicking.

You said 'Do you have any have any criticisms behind these statements? Because you know to be scientific you should criticize the paper...'

I've talked about how there should be an analysis by Paul (2025) alot. Phylogenetic to show that T. rex, T. regina, Nanotyrannus, and T. rex don't collapse into a polytomy), or an ontogram with all of T. rex, ignoring the multiple species hypothesis for the moment, to show that all of Nanotyrannus clusters here, T. regina here, etc. He talks the talk, but doesn't walk the walk, although this has always been a weak point.

I'm not an expert on Tyrannosaurus or affiliated taxa, so no, I can't dive in and find problems like others can. That's why I enjoy the DMG--there are people here who truly know what's going on and can make up for my deficit of knowledge on the esoteric. But even though I don't know the esoteric, there are plenty of basic issues that are apparent even to those who are less informed. If we apply the Dunning-Kruger Effect, I find no reason to reside at the "Peak of Mount Stupid".

Aiden Younk

Carthage College '26

Biology Major // Geoscience Minor

Paleontology Track

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[Franco Sancarlo]

you are very fixated on phylogenetics, 1 a phylogenetic analysis where they put Nanotyrannus outside of Tyrannosaurus has already been done and Paul's study confirms his results (Longrich et Saitta 2024). 2 every phylogenetic matrix in paleontology will give a different result, since more or less weight is given to some characters and the characters change from matrix to matrix, therefore also the results and 3 this in any case does not explain why Paul is wrong. also answering one of your comments "Carr et al.'s (2022) diagnosing Tarbosaurus bataar and Tyrannosaurus rex at the genus rather than the specific level produced unreliable results" is explained in the supplementary material why .

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[Gregory Paul]

Here is the dope on this. 

My reply to Carr et al. 2022 diagnosing at the genus level is my systematics level diagnosis of them, especially the three Tyranno species, at the species level, using all the characters developed in the new paper plus the 2022 study. And I even did a second including on T imp and T rex with reg put into the latter to show that while viable, it is inferior to the 3 species alternative with which I am sure you all agree ha ha. And  I included all the data I had or could dig up for the TT-zone baso-eutyrannosaurs. 

To have gone through all the characters and discussed each and every one would have been a massive text, that when it seems some already think the paper too long if  you can imagine  that. It was not practical. The way it worked was this. I was of course not going to include characters I was not reasonably sure were real. No  doubt you would not have wanted me do otherwise, right? So I only included those from whether my own or from previous publications that I knew from my own examinations and photos, and were verifiable from other photos or figures. And they I could understand (sometimes text descriptions of characters are hard to figure out). If i could not verify a character than I did not include it -- I already had plenty to use so it was  not a big problem. That does not necessarily mean the declined character is not real, but I could not confirm it. I was especially leery of braincase features because I am not up on that.  

The systematics section is a snap shot of the current situation. It has its limits because Jane after a quarter century is not described, the even better Bloody Mary is in the process, Stygi needs a new go over, a host of other baso-eutryannosaurs need work, most major Tyrannosaurus skulls and skeletons are not described (hoperfully someone is working on the exceptionally complete Tufts-Love). There will be a need to compare old eastern Dryptosaurus & Appalachosaurus to neowestern BM, J, P, S and so forth. So I did the best I could with the data on hand to be available for future work.  

No doubt that fully answered everyone's concerns. no? 

GSPaul

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[Riley Shero]

Phylogenetic systematics are key to how we conceptualize evolutionary relationships between taxa, so being fixated on phylogenetics is very appropriate for this subject matter.  Stating that different analyses based on different matrices and methodologies will yield different results is obvious and bordering on tautological, but that doesn't make them useless as methodological tools.  The existence of a single analysis which validates part of a single hypothesis in Paul 2025 (Longrich and Saitta 2024) does not mean that the issue is settled.  That matrix does not address the central claim of Paul et al. 2022 and Paul 2025, which is the existence of multiple species of Tyrannosaurus and which is the hypothesis that has yielded the bulk of the methodological criticisms to my eye.  The question of Nanotyrannus is secondary and is not strictly related to this hypothesis.  Even if Nanotyrannus is eventually found to be valid by other authors, it does not logically follow that there are multiple species of Tyrannosaurus, nor that those species are T. imperator and T. regina as diagnosed by Paul et al. 2022.  The hypothesis of Paul et al. 2022 and its follow-up in Paul 2025 is ungrounded in phylogenetics, and this is a problem for many.  It isn't the only criticism of the methodology used, but its absence presents issues with replicability and the subjectivity of some of the diagnostic characters.  Not all of this is strictly the fault of the author(s) in either case.  A full specimen-level phylogenetic analysis (a la Tschopp et al. 2015 or Malafaia et al. 2025) is impossible because many of these specimens are undescribed and/or privately owned, but in my opinion that is not a reason to charge ahead without a grounding in these or similar methods.

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[Aiden Younk]

In response to Franco Sancarlo:

You said 'fixed on phylogenetics', but I also mentioned an ontogram (ontogenetics). Yes, I'm aware that every phylogenetic analysis is different, which is why they constantly change. Tracking what causes major changes (i.e. the deformation of sister groups, a monophyly breaking into a  paraphyletic group, being placed in an entirely different region of the tree, etc) is difficult.

'Phylogenetic matrices will differ'. Yes, but at this point the matrix should be expanding off of previous matrices. The addition of characters can definitely wipe out topologies. 

'More or less weight is given to some characters'. I'm aware of character weighing and that it can be changed, but characters should remain unweighted to not bias results. If I change the weight of a character that is wiping out topologies to polytomies, that's bias. 

Paul can say his study confirms the results, but where's the proof? His words? He's told us, why not show us? It's like talking about growth series without an ontogram, how do I know you aren't making stuff up? I concur with Riley.

I yield on the 'unreliable results' statement. My mistake.

In response to Greg Paul:

As I said, of course it's fine to not include characters, there's just no explanation of what or how many. Would it have been long? Certainly. Depends how many characters are disregarded. Are people already complaining about how long it is? Yes, but that shouldn't really be a big deal. There's certainly alot to be said.

This statement sets off a red light for me. 'So I only included those I knew from my own examinations and photos, and were verifiable from other photos or figures'. Personal examinations and the literature are obviously great, diagrams can be fine (although I have seen some diagrams that differ from photographs in a non-subtle way). I have heard and been told many times where someone uses a photograph to score a character, then they go and see it firsthand and it is totally different. 

If page limits were the constraint, I would strongly recommend publishing to Palaeontologia Electronica in the future! It's free and there are no page limits. Then you could have supplementary information contain your matrix or characters you disregarded, who published that character, and the basis for discarding.

Another question I have while you're here is what is your basis for assigning sex to some of the specimens of T. regina and T. imperator? You typically need a large sample size, which there currently isn't. Even with a large size, recovering it in a tree can be difficult if dimorphism is subtle. Subadult females, for example, might bleed over into a different growth category. 

Just some concerns of mine, do with as you see fit.

Aiden Younk

Carthage College '26

Biology Major // Geoscience Minor

Paleontology Track

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[Gregory Paul]

To do what you suggest requires goin through every character applied to TT-zone tyrannosaurs since Osborn and Gilmore If I let out any major data set I would be criticized. That means including the 1850 characters in Carr 2020. We are talking maybe 2500 characters. In dozens of specimens. There is no way I could do that.  I have no salery, no grant money, no co-authors, etc. I spend most of my practical time working on popular products that garner income, including the field guides each of which is a massive project including lots of texts, entries, fact checking and rechecking, and one illustration after another, snd indexing, about 1.5 years for each. 

What you think would be useful for me to do is literally impossible. Was not going to happen, never will happen. 

Can you process 2500 characters in dozens of specimens from a host of papers on your lonesome? 

GSPaul 

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[Gregory Paul]

The work on sexes is a preliminary look at the issue in the wake of the work on the orbital bosses which everyone had been neglecting, including me. After being the first to show the remarkable variation in the bosses I was not going to pass up the opportunity to do so. And had I not done so I probably would have been criticized for failing to consider the issue, and with good reason. Hopefully it will get others to look into the matter. Whether it can be resolved on the current limited sample I don't know. 

GSPaul

[Gregory Paul]

A hope RS read the paper and is not just opining on it. I wonder because the study goes to great lengths to separate out the many assorted alternatives. Which is a reason the paper is so long. In Material and Methods --

ETRH, everything is Tyrannosaurus rex hypothesis (which includes the FMTRGH, fish model of Tyrannosaurus rex growth hypothesis) 

MTTH, multiple tyrannosaur taxa hypothesis that includes --

MOTSH, multiple only Tyrannosaurus species hypothesis

MOSTH, multiple only small taxa hypothesis 

ESTNLH, every small taxon is Nanotyrannus lancensis hypothesis

MSTH, multiple small taxa hypothesis 

MTASH, multiple taxa at all sizes hypothesis 

Phylogenetics will have a role to play in the MOSTH & MSTH portions of the MTTH. Not as much as some may think. There is really no way the Bloody Mary with its super elongated, pointy snout skull and elegant hands as long as those of Sue et al. (confirmed by photos with scale bars, one of which shows the arms of the two laid out right next to one another) is going to be a juvenile Tyrannosaurus, all the more so when radically different actual young Tyrannosaurus skulls of similar size are known (Fig. 8). The gradistic differences alone are enough to distinguish taxa at the genus and species level. In this case any cladistics will be to see if BM is a baso-eutyrannosaurs related to Stygi more than the other lithe TT-zone taxa, and maybe if it is close to Dryptosaurus although that is very fragmentary. My paper is not intended to sort that out, that will require description of critical specimens BM, Jane, Petey especially. 

But, as for the MOTSH, phylogenetics is just for show, it is not likely to actually show us anything. These are very closely related intragenera sibling species that will cluster together at the end of any tyrannosaur cladogram. We already know that. The characters are not going to tell us much about how they are interrelated. Retaining the two small incisors typical of tyrannosaurids early T. imperator is likely to prove basal to the other two, but we already know that. There is probably no means of telling if anagenesis and/or cladogenesis is involved regarding the other two species. In any case cladistics in such a situation is inferior to diagnoses via comparative anatomy. In any case sorting that out was not the purpose of the paper, doing the basics of showing the presence of multiple Tyrannosaurus species via the preponderence of the data is. 

I did what I could with the data on hand and my abilities. If people don't like the absence of phylogenetics OK. but stop whining about the papers and get out there and do something about it by doing them yourselves. Take the data I published, and perhaps that of L&S, and see what happens. If you don't trust my data then do your own work. Do that long long list of characters examining each and every one by me, L&S, Larson, Carr. Or don't do your analysis until BM and J, etc. are described. Have some some paleophylofun. Complaining is easy, better to do what you think should be done and get it through peer review and I am available as a reviewer.  

If one uses all 1850 characters in Carr 2020, plus other data sets including mine and Longrich and Saitta and Larson for something like 2500 total, and assesses them in a few dozen specimens, well that's tens of thousands scores. Is that even practical? I suspect the Zanno team is doing an extensive character analysis. It will be interesting to see how many characters they wade through and hwo many specimens. And will they do a listing of results for each character as has been suggested I do on my own? We shall see. 

What not to do is what Carr and company did such as complain about the sample size being too small when it is actually on the large side for dinosaurs, then lecture about using private specimens which will decrease the sample size if removed, and then use that data to try to disprove Paul et al. 2022. Then ccompare fossil elements to modern taxa which is comparing apples to oranges, and the modern data may contain captive raised birds which is a big no-no. Then complain the Paul et al. 2022 used on 2 characters which would be OK if it did for taxa at this close level, and it was actually 7. And get the incisor thing wrong in multiple ways, including saying we ratios derived from different sides which is nonsense. And then not present actual positive evidence that the very different TT-zone specimens somehow are actually one species despite that breaking amniote, reptile and tyrannosaurid norms and requiring some sort of metamorphosis and the growth curves not matching up. Well you all get the drift. 

GSPaul

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[Thomas Carr]

The Jane monograph is completely written; the line drawings are still in progress

-TDC

[Milo Gaillard]

To Thomas Carr:

That’s great news. I can’t wait for the monograph to be published. Jane is a very important specimen.

Thank you,

-Milo Gaillard

On Mon, Jul 7, 2025 at 07:48 'Thomas Carr' via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com> wrote:

The Jane monograph is completely written; the line drawings are still in progress

-TDC

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[Aiden Younk]

Greg Paul states: 

'What not to do is what Carr and company did such as complain about the sample size being too small when it is actually on the large side for dinosaurs, then lecture about using private specimens which will decrease the sample size if removed, and then use that data to try to disprove Paul et al. 2022.'

Greg is correct in both points, but at issue here is that in order for Carr & Napoli et al. (2022) to adequately test Paul et al., they had to use your data, which included private specimens. They met you at your level and were forced into a corner because, otherwise, you and your cohort would have hopped all over them for excluding those privately owned specimens. Even still, they got different results. 

I'll quote you from your new paper; "The inaccurate claim...should not have been stated, and must never be repeated."

Aiden Younk

Carthage College '26

Biology Major // Geoscience Minor

Paleontology Track

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[Riley Shero]

To Greg Paul:

My email was a specific address to the complaints of Franco Sancarlo, which appeared to be of the opinion that the entire hypothesis hinges on the validity of that taxon specifically.  My goal was to dispel that misconception, not an attempt to address all of the many claims and hypotheses in the paper as a whole.  I have read the paper and I am aware of the multiple hypotheses that were suggested, and I also read the materials and methods section.  I was addressing specific points of contention by another person in this email chain.  I'm not interested in comprehensively addressing the paper itself, which will be done in the literature in the coming months and years.  I'm also not interested in litigating the methods of Carr et al. 2022, because even if the methods in that paper are shoddy (not saying they are, but for the sake of argument) it does not therefore follow that the conclusions of Paul et al. 2022 are correct by default.  Each hypothesis must stand on its own merits, not necessarily on the merits of every specific criticism thereof.  The criticisms I raised of the MOTSH exist outside of Carr et al. 2022 and will persist in the literature, I suspect, and the precise taxonomic status of Tyrannosaurus will not be resolved in this email thread.

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[Gregory Paul]

The dinosaur list was limping along just a year or two ago. It's back baby! 

GSPaul

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