Eutyrannosaur preprint

[Franco Sancarlo]

Preprint: Sancarlo, F. & Paul, G. S. (2025) The taxonomics of the diverse, lithe basal eutyrannosaur genera and species of late Maastrichtian western North America. BioRxiv (https://doi.org/10.64898/2025.12.10.693447)

Hi everyone. We have posted this bioRxiv draft of our analysis of the situation with the lesser TT-zone tyrannosaurs in the wake of the recent Longrich & Saitta, Paul, Zanno & Napoli and Griffin et al. papers on the subject. With the taxonomically rigid ETRH now moot the phylogenetics and taxonomy of the creatures is now, as it should be, open to free scientific discussion and debate in the context of the MTTH Gilmore proposed back in 1946. 

 

The profile skeletal of the complete Bloody Mary is incomplete because much of the skeleton (some of which was damaged by inept excavation until Peter Larson took over) is covered by matrix that includes soft tissues. The proportions including the small skull are after the photos and measurements in Z&N, etc. BM looks bigger hipped than Jane and was probably a little heavier. 

 

Although L&S and P agree with Z&N that the ETRH is not operative, the first two papers agree that the long armed baso-eutyrannosaurs are not all Nanotyrannus, even the two intraspecies indicated by Z&N not being adequate. P in his paper– who emphasizes the danger of making Nanotyrannus into yet another taxonomic wastebasket -- considered alternatives, but did not go further because we all awaited the description of Bloody Mary (not realizing how soon that would be:). The senior author of the preprint decided in the summer that BM and Kane are new genera, and P joined in the effort to detail why. 

 

As Fig. 7 shows, the intragenera sibling species of Allosaurus look pretty much alike. Same for those of Daspletosaurus. Tyrannosaurus species are more diverse which is why chucking them all into T. rex is not viable (a point that Z&N acknowledge may be correct, as do N&S, so get ready for T. rex not being special anymore – this is the first study to use the new specimen # for Stan:), but they are still fairly consistent. Grade is of course very important when it comes to determining genera.

 

A little while back N asked P on this list to not name Bloody Mary until it is more completely described in a future study. Z&N did name Jane before it has been described. Not a complaint, we were going to name Jane before Z&N did so at the species level. Note that folks can cite this study in technical papers -- Z&N cite Napoli’s bioRxiv item on gator growth. 

 

With Bloody Mary now published it can be seen just how dramatically different it is from both Nano and Jane in its much lower skull with a sharp apex to the snout, high tooth count, and other details. As Z&N note Stygivenator is a very bad holotype, but it exists and it needs to be assessed and diagnosed on its own, rather than lumped into Nano that it is very distinctive from. What is close to Stygi in form and placement is BM, so much so that the two appear to form their own clade at the subfamily level. At the same time there are differences that indicate they are not the same species or even genera. So we name BM “Elegansvenator zannoae”. 

 

A reason we are doing this now is because we are very, very nervous that someone else will conclude the same and name BM, so we are posting the preprint to stake a claim. Same for Jane (which we were already preempted on by Z&N at the species level). 

 

Which also is not Nano. For starters there are considerable differences between what is preserved of Nano and Jane. To that add that we do not really know what the postcrania lacking Nano actually is – it is a better holotype than Stygi, but not by much. Unlike gracile BM and Jane which cannot be late Maastrichtian Dryptosaurus because the robust limbs of the latter are so different, Nano could be in the same species, genus, or family as the NJ specimen. Or very possibly not. But this is a reason that Nano is such a bad holotype that putting other fossils into should not be done unless there is very good reason to do so. So Jane is named “Gilmorelarsontyrannus lethaeus” for reasons that are also obvious – Gilmore was the researcher who using standard comparative anatomy and ontogeny proved the MTTH, and Peter L did the most to defend it of late.  

 

Some of the features Z&N cite as characteristics of Nanotyrannus may instead be subfamily or family attributes. 

 

In his paper P explained that the long arms probably originated in Appalachia and moved into the American west, an item repeated by Z&N. This helps explain the high diversity of tyrannosaurs great and small in the TT-zone, and there is growing evidence that tyrannosaurs were more diverse in a given formation than has been realized as noted by Z&N. For example, the Nanxiong Formation has two small and at least one big tyrannosaur. And of course the TT-zone was deposited over over a million years, and these genera and species did not all live at the same time.  

 

We also take a broader look at the ETRH v MTTH. It is patently obvious that super lithe Elegansvenator and Gilmorelarsontyrannus are not juveniles of mighty Tyrannosaurus. Those of the latter would have been stout little beasts like those of its close relation Tarbosaurus (which Carr thinks is the same genus which is plausible). This is supported by what is known of the juvenile Tyrannosaurus fossils, such as the not elongated tibia of Baby Bob and the robust dentaries. The NYTimes article on the Z&N paper actually says there still no baby Tyrannosaurus fossils, when there are seven of them. Juveniles within a species show little variation, it is with maturity that variation may appear, as per sexual dimorphism. With the amount of anatomical variation in the lesser TT-zone fossils sufficient to support multiple taxa the idea that they are all juvenile Tyrannosaurus flies in the face of vertebrate ontogeny. 

 

About the news coverage of the subject, it is peculiar that aside from Z&N, the long term advocates of the MTTH were rarely interviewed. It has mainly been the ETRH folks. This is a circular bias of the media that abetted to ETRH even though it was always seriously flawed since Rozhdestvensky mentioned it in 1965, and it became oddly ardently held as the “establishment viewpoint” at the turn of the century. 

 

We will soon submit the paper for peer review. This is a draft and we are working on additional aspects, if any wish to direct our attention to items and suggest changes please do so in the near future. 

 

Franco Sancarlo

GSPaul

[Tyler Greenfield]

I highly recommend that you upload a revised version of your preprint with the new genus and species names redacted, since it is not a published work. See Recommendation 8G and Article 9.9 of the International Code of Zoological Nomenclature.

On Dec 13, 2025, at 1:27 PM, Franco Sancarlo <franco.sa...@gmail.com> wrote:



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[James Napoli]

Jesus fucking christ

[Isaac Wilson]

This ought to age well.

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[Gregory Paul]

Three new species in the Onygenaceae isolated from marine sediments of Chinese seas: A. sedimenticola, C. microsporum, and C. sphaerospermum. https://www.biorxiv.org/content/10.1101/2023.12.31.573767v1.full

Six New Species and Two Reinstatements of Viola (Violaceae) from China

https://www.biorxiv.org/content/10.1101/2025.10.02.679011v1.full.pdf

This is a quite common practice in bioRxiv, so not sure what the problem is. 

Of course the names do not yet meet ICZN criteria, we are working on the version for peer review. 

[Tyler Greenfield]

It does not become good practice just because others have made the same mistake. My point still stands.

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[Franco Sancarlo]

you are Tyler, we should have thought about that before. I did not knew about the rule, thank you very much

Privo di virus.www.avg.com

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[Adrian Boeye]

Given the importance placed on postorbital horns, I'm particularly surprised that UWBM 99000 hasn't seen any mention consider that it preserves excellent post orbitals and shows off some pretty significant variation in rex specimens. Ideally would want  to see some more quantitative analysis attached to this kind of work though

[Franco Sancarlo]

Very good comment, but Paul (2025) talked about the argument way better than this preprint does

Paul (2025): https://doi.org/10.11646/mesozoic.2.2.1

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[Mickey Mortimer]

First, good job noticing that "The origin and evolution of the tyrannosaurids" from 1995 was coauthored by Ford and Yamamoto. Everyone (including myself) seems to have missed that, which affects a wide array of names like Tyrannosauria, Dinotyrannus, Jenghizkhan, Stygivenator, etc. that have generally just been attributed to Olshevsky, 1995. I notice Ford's and Yamamoto's names were left off the English translation, but the Japanese original says "George Olshevsky & Tracy L. Ford Seiji Yamamoto" right there on page 92. And that's how both Ford currently ( http://www.dinohunter.info/html/1990/articles1995.htm#Theropoda ) and Olshevsky did (e.g. 2000's Mesozoic Meanderings #3) cite the names. 

I noticed this though because you incorrectly call Tyrannosaurini a subfamily when it is a tribe (a mistake you made in your 2025 paper as well). The same goes for your supposed subfamily "Elegansvenatorini". With that suffix it's a tribe, or else you should call it "Elegansvenatorinae". 

Also, you list Nanotyrannus lancensis as valid, a junior synonym of "Elegansvenator" and a junior synonym of "Gilmorelarsontyrannus", and Stygivenator molnari as both valid and a junior synonym of "Elegansvenator".

Mickey Mortimer

[Gregory Paul]

Ah, yes, UWBM 99000 does indeed have like way cool postorbital bosses:) As I discuss and illustrate (Figs. 2, 4, 5, 6) in my Mesozoic paper linked below. It like bigger Scotty are the only Tyrannosaurus specimens with those prominent, high set discs sort of like Mickey Mouse ears. They are both stratigraphic high set robusts, and finally show us what actual T. rex really looked like (the type is missing the postorbitals:(. Which is way different from earlier T. imperator such as Sue with their -- very atypical for tyrannosaurs -- massive, long spindle bosses. Classic species identification features. So using Sue to illustrate the last Tyrannosaurus bad, same for showing T. rex hunting early Triceratops horridus. 

The preprint is largely about the small TT-zone tyrannosaurs, and the final paper will should be the same. I do not have current plans to return to the subject in a big way, having done do in the Mesozoic paper, with some catch ups in the newer work. Will be interesting to see what develops in the fairly near future. 

GSPaul

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[Gregory Paul]

Interesting point. I was sort of wondering about the naming of Stygivenator etc. So I finally did a dope slap and asked Ford, and he told me the correct author citation. 

Thanks for the comments on the assorted names. 

GSPaul

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[Franco Sancarlo]

Thanks for pointing that out. It was a careless mistake on my part.

[Adrian Boeye]

While UWBM 99000 may have more pronounced post orbitals, but I hesitate to draw conclusions with other rex specimens like FMNH PR 2081. FMNH PR 2081's skull had some pretty famous taphonomic deformation and the actual restoration of the skull was done quite some time ago. It's probably a point for another day but aren't display characteristics also notoriously variable?

Will be sure to look over the preprint more though, nanotyrannus lancensis and lethaeus are certainly some interesting study animals 

[Franco Sancarlo]

Great comment again, for the display part Paul (2025) talked about it, he take many more specimen! 

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[Gregory Paul]

The postorbital bosses on both sides of Sue are the same, there is no sign of there being distorted on the actual skull. And other specimens also low in the TT-zone have spindles, which are not seen high in the formations. The only tall discs, Scotty & Tufts-Love, are on robusts from high in the zone. None of the graciles, T. regina, has them. So the correlation is in line with multiple species. Plus there is no other tyrannosaur species, or theropod species, that has such variation. Heck, there is more variation in Tyrannosaurus than all other tyrannosaurids combined. 

I get the sense you have not read the Mesozoic paper (which has nearly 10K looks so far). If not then best to do so and then come to conclusions. 

GSPaul

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[James Napoli]

Now that I've had time to fully read this, I will note two things for any interested party:

1)  On page 15, you write "Bones have been carefully traced from source images -- any who disagree with their accuracy need to demonstrate each of the errors with comparative images." I'm happy to do so. To start, you illustration of CMNH 7541 is replete with fundamental errors. You illustrate only small portions of the mandible, premaxilla, and maxilla as being missing. Even a cursory glance at the CT imagery presented by Witmer & Ridgely (2010) - or the illustrations in Carr (1999), for that matter - should indicate that far more of the skull is reconstructed, and that there is in fact a fracture running through the entire width of the rostrum that breaks the skull into two halves. You similarly illustrate the dorsal surface of the lacrimal as flat, but the cornual process was clearly present and broken off, as indicated by the presence of a large lacrimal vacuity on the right side of the skull. The lacrimal is also missing its rostral ramus, which you illustrate as present, because you've mistaken the nasal for the lacrimal. You illustrate the maxilla as having a large dorsal convexity (the "maxillary flange" in tyrannosaur parlance), which is clearly absent when working on the specimen itself. And of course, you have not restored the original length of the caudal part of the skull, which is crushed inwards (as reflected by the broken quadratojugal flange). The figures in Witmer & Ridgely (2010) make these points obvious. 

Your restoration of NCSM 40000 also has a number of clear errors. You illustrate the premaxilla as lacking a rostral "upturn", but if you had examined our figures closely, it should have been clear that the premaxillae are displaced from their natural position, and that if re-articulated they would be more reminiscent of the condition in all other Nanotyrannus specimens. It seems that your interpretation of the extremely shallow rostrum in NCSM 40000 is an artifact of deformation to the right maxilla, which has a clear fault in the pila interfenestralis indicating that it has been dorsoventrally "telescoped". The left maxilla is better preserved, in this respect, and further shows that the rostral end of the antorbital fossa is not, in fact, highly acute - this condition, too, is the result of damage. I cannot determine why you show some teeth as present and others as missing, when the distribution of teeth you illustrated matches neither side of the specimen. All of these factors are clearly evident in the figures we published.

2) You have repeatedly brought up the fact that we named Jane as if it justifies the current study, but there is a crucial difference between you work and ours. We were given explicit permission by the Burpee to study Jane as part of the Dueling Dinosaurs project, and in fact were given permission to loan her skull and fully CT scan it. When we determined that Jane belonged to a new species, we alerted the Burpee Museum prior to publication. Jane is (to our knowledge) still being described actively by Carr et al., and we strove to limit our illustration and description of Jane as much as possible to protect their priority on a full description.

You were not given explicit permission to work on NCSM 40000, and in fact, I conveyed a request on the DML to you to refrain from taxonomic action without all of the relevant data we were generating with work in progress. You refused this request and, as noted above, made myriad basic anatomical errors in your rush to get "your names" published. Correcting these errors would, of course, significantly weaken your argument that these animals warrant placement in new genera, and your argument that NCSM 40000 is not Nanotyrannus lancensis despite possessing an autapomorphy of that taxon. 

The anatomical errors throughout this work should make it clear to any others in our community that the authors did not study any of the relevant material firsthand, and they have stated repeatedly that the preprint exists only to stake claims on naming rights for the specimens that they did not collect, prepare, acquire, or even have permission to publish on. In my opinion, this is an an unethical manuscript and an act of taxonomic vandalism. I suggest you take any actions available to you to retract this preprint and that you do not submit this work for peer-reviewed publication. 

On Saturday, December 13, 2025 at 8:00:22 PM UTC-5 Gregory Paul wrote:

[Milo Gaillard]

To James Napoli,

Thank you for calling out Greg Paul for his nonsense. He seriously needs to stop this.

On another note, “Gilmorelarsontyrannus” is the single worst proposed name for any reptile taxon that I have ever seen.

-Milo Gaillard

Sent from my iPhone

On Dec 13, 2025, at 19:59, James Napoli <jamesg...@gmail.com> wrote:

Now that I've had time to fully read this, I will note two things for any interested party:

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[Gregory Paul]

Thanks for the comments on the skull restorations, we posted the preprint in part to get feedback, which we will take into account. Some points. 

We did not illustrate Nano has not having a lacrimal hornlet when it was alive. To explain, in black around white profile-skulls, as in the same for profile-skeletals, the black can represent missing bone, as per the anterior prong of the combined squamosal-quadratojugal of Nano, much of the antorbital fossa, and so forth -- likewise many of the skeletals in the paper have lots of black where bones are missing. The preserved Nano skull lacks the hornlet, so its presence is represented by the solid black bump, approximated after that of Jane. I do not show bone cracks in profile-skulls-skeletons because those who might not know the anatomy could mistake them as bone sutures (I do not show the cracks in the nearly complete nasal of the LACM juvenile in Fig 9G for instance). As far as we can tell the Nano maxillae were not longer than how they are restored in the skull, so no need to show a gap. Perhaps James disagrees, and we are interested to see his upcoming restoration. We will take another look at what bones are missing vs present -- note that the restoration uses both sides to fill in the left view. All that said, there are already on hand numerous diagnostic characters that indicate that Nano, BM, Stygi etc are not the same taxon -- the way tall quadrate-quadratojugals on Nano compared to the much shorter ones on both sides of BM for instance. As they say, perfection is the enemy of good enough, and perfection is rare in fossils. 

As for BM, the teeth are, as in the other skulls, from both sides to fill in the left view. Shall consider doing a revised or new version based on the comments, but those two maxillae are not all that diff from one another. It's a way low skull. Again, as is the differences with the other skulls are already abundant. Much more diff between BM and Nano than between D. torosus and D. horneri, or A. fragilis and A. jimmadseni. What I am wondering is about the seeming flexion at mid skull in which the snout is downflexed from the temporal box. Is that real, preservation distortion, damage before Larson took over? If real could be a diagnostic character. 

Now. As for the assertion that people are still severely restricted in what they can do regarding BM, now that's a head scratcher. Once a detailed publication appears on a fossil the analysis horse is out of the research barn and others can do what they wish. That's basic procedure, I do not think there has been another case of a describer telling others they cannot do what they wish with the specimen after it appears in a well documented peer-reviewed study. There is not a need to know more about BM for researchers to make deep conclusions about its nature. The Nature photographs are high quality. The specimen is actually not super informative in some regards. The complete caudal series is badly banged up (I think from the initial collection effort before Larson arrived), and the whole series is photographed. Most of the rest of the vertebrae and ribs are still under sediment. Good lateral pics of the skull in the paper. Cannot see the top but that is not critical (all the more so because the tops of Nano and Jane are lousy). Very nice pics of the arm. Pelvis and legs in view. Lots of juicy text description. Key measurements published  (still not for Jane) and the scale bars look correct:). I do not see what vital points I would discover by seeing the specimen (until more is prepped well into the future, which I assume will be covered in additional studies down the line). Anyone is now free to name BM, and Franco and I are very nervous someone else will soon do so at least at the species level (in Nano or Stygi), we have our reasons to think that. 

To put it another way, if I worked long and hard to describe a new specimen and peer review published it in detail, and put it in a previous genus-species, I would not even think of telling others to not name it until I do another paper on the specimen. Just not done. 

And what is this about how one has to examine a specimen before publishing on it? Really? Great to do such, but not necessarily necessary, or always practical. Say a taxonomic analysis of a group includes specimens located somewhere in Siberia, others in far western China, and more in south-central Africa? They have been documented in publications. Have to see them? This attitude common to people who have the supporting budget (soon probably disappearing and time to travel hither and yon can come across as a way to push out those who do not have that ability. Just saying. 

About the Gilmorelarsontyrannus name everyone is just so giddy enthusiastic about. I was thinking of naming Jane in the Mesozoic paper, but was not really into doing new names in that, and figured no one else was going to do so like duh (Carr and others thinking it is T. rex, others. N. l.), so why not wait? When Franco said that it and BM needed titles in the summer we were going to tag it Gilmoretyrannus larsoni, we want to honor the two who invented and then have so well defended the MTTH. To our surprise (both in how soon it came out, and that they did it not that we disagree that Jane is not N. l.) Z&N gave it a specific name, so that is out. Thus the fabulous genus name. Right?  

GSPaul  

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[Jaime Headden]

Adrian Boeye wrote:

> It's probably a point for another day but aren't display characteristics also notoriously variable?

It's a point for now, since it should be addressed in any paper that seeks to use them as significantly diagnostic, given arguments of variability.

Let's address them now, in a way, as a jumping off point for this pre-review manuscript:

To be taxonomically informative, they must express continuously with other portions of anatomy also deemed taxonomically informative. Prior to this, arguments of Nanotyrannus's taxonomic affirmation were based on features others considered ontogenetically variable, or unexpressive in a supposed adult, which previous studies had argued that the Cleveland skull and Jane (later) weren't. [And they remain non-adult, but "near," which still makes them subadults.] Let's say we're tabulating each bone for each specimen for which diagnostic features have been argued, such as femora, ischia, maxilla, mandible, and postorbital, say, including vertebrae. Analysis of these features should be plotted by scale and mass estimates. I'm sure Greg has the latter in hand, given the first paper on this subject in 2025, although it did result in some issues that Mickey Mortimer pointed out back then regarding expression of cranial features in specimens sorted in one or two of various species Greg named. That is, despite this work, the features, and specimens, weren't sorting well.

When that happens, that feature can be said to be of reduced, if no, taxonomic value. If, rather, these features are size-dependent, then it's more likely they are ontogenetic, or even sex, related, both of which have to be ruled out before one can make arguments for taxonomy.

As for the actual point of Adrian's comment:

Variable cranial features can be useful taxonomic indicators, if there's a good enough sampling. I am less heartened agreeing with cranial features likely related to sociosexual behavior and signaling when, in ceratopsids, the use of P1 and P2 loci can express variably left to right. Once, curvature of the nose horn mattered; now it doesn't; then it was whether there were brow horns or not in chasmosaurines. Likely, variation exists, but there can be constraints, but also overlap among taxa, suggesting then that while there is utility, it is of diminished value. That is, if there's enough support for taxonomic separation of species without postorbital boss shape, mass, or other expression, and the bosses then support that variation when included in the dataset, THEN there's value in such things.

Cheers,

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Jaime A. Headden

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

[Gregory Paul]

Not entirely clear about the below, so here is some clarification. 

Franco and i are not trying to use display features to help determine and diagnose the small baso-eutyrannosaur taxa, nor did Paul's Mesozoic paper this summer. They don't have much in the way of such features, and the sample is small. It is possible something could be done, BM may have a different lacrimal hornlet than Jane, but the item is missing in Nano. 

As for Tyrannosaurus, there is a VERY extensive discussion of the issue in the Mesozoic paper (https://doi.org/10.11646/mesozoic.2.2.1) which takes into account maturity, sex and so forth. A very preliminary effort to use the postorbital bosses to determine sex is made -- that I did so is being criticized: had I not done so I would have been criticized for not doing so, can't win on these things. The Tyrannosaurus sample is substantial, the variation is as documented very extensive being way more than in other tyrannosaurid species and even genera or all tyrannosaurids combined (which I explain why), the variations correlate significantly with stratigraphy. The S&P paper merely touches upon the issue, the focus of the paper being on the baso-eutyrannosaurs, not Tyrannosaurus. To see the later you have to take the time to read the Mesozoic paper.   

GSPaul

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[Richard Sutton]

I've seen Tracy Ford cite "Olshevsky vide Olshevsky, Ford & Yamamoto, 1995" before too (here). From what I can gather, Olshevsky is the sole author of the articles with Ford providing skeletal illustrations, and Yamamoto providing illustrations of the animals in life. 

Richard Sutton

Undergrad

York University

[Mickey Mortimer]

Yeah, but I would only use 'vide' in a situation where a taxon was explicitly credited to only one author, as happened sometimes with Nessov in his coauthored papers. And even if Ford and Yamamoto had no textual input, I'm sure we all know cases where authors are added to papers who did far less than draw pictures.

Mickey Mortimer