Tyrannosaurus rex maximum size + titanosaur postcranial pneumaticity + hadrosauroid eggshell from Late Cretaceous of France

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

New papers:

Free pdf:

Jordan C. Mallon & David W. E. Hone (2024)
Estimation of maximum body size in fossil species: A case study using Tyrannosaurus rex
Ecology and Evolution 14(7):e11658
doi: https://doi.org/10.1002/ece3.11658
https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.11658

Free pdf:
https://onlinelibrary.wiley.com/doi/epdf/10.1002/ece3.11658



Among extant species, the ability to sample the extremes of body size—one of the most useful predictors of an individual's ecology—is highly unlikely. This improbability is further exaggerated when sampling the already incomplete fossil record. We quantify the likelihood of sampling the uppermost limits of body size in the fossil record using Tyrannosaurus rex Osborn, 1905 as a model, selected for its comparatively well-understood life history parameters. We computationally generate a population of 140 million T. rex (based on prior estimates), modelling variation about the growth curve both with and without sexual dimorphism (the former modelled after Alligator mississippiensis), and building in sampling limitations related to species survivorship and taphonomic bias, derived from fossil data. The 99th percentile of body mass in T. rex has likely already been sampled, but it will probably be millennia before much larger giants (99.99th percentile) are sampled at present collecting rates. Biomechanical and ecological limitations notwithstanding, we estimate that the absolute largest T. rex may have been 70% more massive than the currently largest known specimen (~15,000 vs. ~8800 kg). Body size comparisons of fossil species should be based on ontogenetically controlled statistical parameters, rather than simply comparing the largest known individuals whose recovery is highly subject to sampling intensity.

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Blog:

On the trail of giant Tyrannosaurus rex

https://archosaurmusings.wordpress.com/2024/07/24/on-the-trail-of-giant-tyrannosaurus-rex/

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News:

Scientists assess how large dinosaurs could really get

https://phys.org/news/2024-07-scientists-large-dinosaurs.html

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Virginia L. Zurriaguz (2024)
Variation in the postcranial pneumaticity in derived titanosaurs (Dinosauria: Sauropoda)
Historical Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2024.2377708
https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2377708


Currently, only birds have a pneumatic system, but in the past, this was common among several ornithodirans. Within Titanosauria, it was the saltasaurines that showed a high degree of postcranial pneumaticity. The objective of this work is analysing the extent of postcranial pneumaticity in saltasaurines and compare it with other derived titanosaurs. To carry out this work, presacral vertebrae, dorsal ribs, scapulae, coracoids and ilia of saltasaurines were analysed. The presacral vertebrae present a high degree of pneumatisation with a highly variable distribution of foramina, with some ‘foramina zones’, there is a homoplastic pattern of pneumaticity: presence of foramina connected to camellated tissue. With respect to the ilia, camellated tissue was recorded in all taxa. Instead, scapulae and coracoids, present camellated tissue in Saltasaurus and they cannot be pneumatised in Neuquensaurus. Comparing with other titanosaurs, we observe that there are ‘foramina zones’ for presacral and caudal vertebrae. It is also possible to establish that the pneumatisation of the dorsal ribs has a conservative pattern, not only in saltasaurines but also in the Saurischia clade, and the presence of pneumaticity in the ilia is frequent in the Lithostrotia and even outside, in rebbachisaurs.

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Paraspheroolithus porcarboris oosp. nov.

Tom T.P. van der Linden, Darla K. Zelenitsky, René H.B. Fraaije, Géraldine Garcia, Xavier Valentin, Femke M. Holwerda & Anne S. Schulp (2024)
The first hadrosauroid eggshell from the Aix-en-Provence Basin (Late Maastrichtian) of France
Historical Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2024.2380808
https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2380808


Nearly all dinosaur egg or oospecies occurrences from the Upper Cretaceous of France have been attributed to titanosaur dinosaurs. Here, we describe the first occurrence of probable hadrosauroid eggshells from France, which we assign to a new oospecies, Paraspheroolithus porcarboris oosp. nov. (oofamily: Spheroolithidae), from the upper ‘Argiles et Grès à Reptiles’ Formation (upper Maastrichtian) of Aix-en-Provence. Paraspheroolithus porcarboris differs from all other spheroolithid oospecies in the following combination of characteristics: prolatospherulitic morphotype, prolatocanaliculate pore system, prominent anastomosing ornamentation, medium eggshell thickness, less defined horizontal accretion lines and high pore density. The spheroolithid affinity places the new ootaxon outside oofamilies ascribed to titanosaurs (i.e. Megaloolithidae and Fusioolithidae), and thus its discovery expands the parataxonomic diversity of this region and formation. We suggest the taxonomic affinity of Spheroolithidae is somewhat broader than Hadrosauroidea, potentially encompassing all Ornithopoda. However, a hadrosauroid affinity remains the most plausible for Paraspheroolithus porcarboris based on the absence of other ornithopod remains from late Maastrichtian deposits of the Ibero-Armorican Island.

[Gregory Paul]

~9 t is way too big for known Tyranno, the three largest know specimens (Sue, Stan, Scotty) all being ~7.5, their volumes being well documented and the SGs around 0.96 based on ratites without thin walled limb bones. And world record specimens being almost twice normal mass is pushing it at best, 10 being more likely. And T. rex of course makes up only a third of the known specimens not that that matters much. 

GSPaul

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[Adrian Boeye]

This study is definitely quite interesting and provides exciting insight on size and population dynamics, and of course just thinking about a predatory animal reaching that size and how it would live is incredible. I am not familiar enough with equations about population to make any statements other than reading over the paper and that the general results and conclusions seem well supported by the presented evidence. That said, biomechanically, functionally, and ecologically a 15 tonne Tyrannosaurus is extraordinarily interesting. Taking a quick look at biomechanics, even at low FR numbers, just due to sheer size we could expect surprisingly quick speeds (using some guesswork for overall dimensions, at FR 1 a 15 Tyrannosaurus would move at ~6 m/s or a GRF of 1.8 BW). I would theorize that anything faster is dubious since the amount of force needed to propel that much bulk at speed is staggering, to say nothing of the need to support the animal from the impact force produced by higher speeds. However, a competent power walker cruising at a reasonable speed seems entirely plausible. Something the paper mentioned that was particularly interesting was the potential for these truly giant Tyrannosaurus to target sauropods. For young, old, sick, or weak sauropods, crossing paths with a 15 tonne Tyrannosaurus would likely be exceptionally bad news since their primary defensive option of being bigger than any potential attackers is fairly diminished. Young sauropods would be in exceptional danger since the advantage of size would probably be flipped in favor of the predator. I think it is also safe to say that a young sauropod is not going to be winning a footrace with an attacking Tyrannosaurus which likely worsens the young dinosaur’s odds of survival. This is a fair amount of speculation on my part but seeing some of these battles between these giants would be incredible, if probably quite violent and messy. 

While a lot of my thinking above is educated inferences, I hope that if/when one of these truly giant Tyrannosaurus specimens is unearthed we get to see an influx of material on it. At the very least, I think most of us can agree that these kinds of articles (and potential future validation by a discovery in the future) are exciting, especially so for youth who may become the next generation of paleontologists. 

On a bit of a tangent, Dr. Paul you mention a mass of 7.5 tonnes for some of the bigger adult Tyrannosaurus specimens and I've seen this figure discussed a few times. I've done some cursory searching, however I have been unable to find an exact reference with the attached figure. If possible and it is not too much hassle, do you have a link or reference where I can find this figure? I am always interested in mass restorations and the broader functional and ecological implications they may hold for an animal and how it lived, doubly so if the restoration has information about musculature. 

Best,

Adrian

[Gregory Paul]

The figures are in my BioRxiv post on the species of Tyrannosaurus, and the Princeton Field Guide to Dinosaurs 3rd edition. The details of the mass estimates are in the weight table at the Princeton University website for the book. 

GSPaul

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[Adrian Boeye]

Thank you for pointing me in the direction of the original source material, it is definitely quite interesting and serves as an interesting contrast to some of the heavier restorations I have seen. 

Best,

Adrian

[Gregory Paul]

Arch predators are lean mean fighting and killing machines built for speed and agility, they are not bulky fat laden klutz's. That some researchers and illustrators do not seem to understand this basic biological reality is perturbing. Any restoring ballooned gastralia baskets are restoring the animal bloated after death, or gorged after feeding on a large carcasse. 

The top view of Sue is with the illustration in the field guide. Doing comparative top views of the differing specimens is problematic because of distortions of the ribs and lack of documentation of them aside from Sue. I have no idea what the ribs preserved for good old 5027 even are. And what happened to Stan? 

We will never know what the biggest Tyrannosaurus were like because being super rare they will never ever be found. The possibility that they were fossilized at all much less in a reasonably complete state is very very very low. They if any were preserved that they will happen to be at the surface and found by humans is super duper low. 

GSPaul

https://groups.google.com/d/msgid/DinosaurMailingGroup/9b3fbc20-c81d-48cf-9d22-704595b522c9n%40googlegroups.com

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[Leo Sham]

I would like to rephrase Greg's "we will never know" statement a bit. While statistics may allow us to estimate a maximum size that could have been attained by a "significant portion" of _T. rex_ (and how much is significant? the top 1% of population throughout the species' lifespan?), it will not allow us to know the size of the figurative Guinness Record holder (someone exceptionally old and exceptionally lucky, or someone with hormonal tumor?) that simply baffles statisticians. 

That said, will we be satisfied by accepting the size (range) of "the top 1%" as maxima? Then what are world records for?

[Ethan Schoales]

Of all the T. rexes that ever lived, one must have been the biggest. Even if it did get fossilized, though, too bad it doesn’t come with a label saying “THIS IS THE BIGGEST EVER”.

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[Jordan Mallon]

Boy, it's been probably 20+ years since I last posted to the DML... good to be back!

The mass estimates Dave Hone and I used in our paper were derived from femoral scaling methods, which are more widely applicable than volumetric-density methods and so offered us a larger sample size to work with (important when doing stats, deriving growth curves, etc.). Regardless of the absolute size estimate, the distribution about the growth curve stays the same, so our conclusion that the maximum possible T. rex was 70% larger than the largest currently known still holds, though the baseline size may shift with one's methodological preference.

Greg, I thought it was interesting that our 15,000 kg max size estimate perfectly lined up with yours for the "largest unpreserved world record individual predatory dinosaurs" (taken from your 1997 Dinofest paper). I'd be curious to know how you came up with that number.

Jordan

[Gregory Paul]

In the 1997 paper I note that world record animals tend to be twice the average adult mass, so the reason for the 15 tonne biggest theropods estimate was explained. But the references were not ideal and may produce an excessive maximum/average ratio. In my field guides I note a lower ratio. 

It is interesting that all three biggest Tyrannosaurus specimens, each representing one of the three species, is about 7.5 tonnes. It is possible that being active predators the genus was constrained in size. I do not know if any shed teeth indicate larger specimens. On the other hand there are Triceratops specimens up to 10 tonnes. 

Because bone dimension scaling is not reliable, it should be corrected by volumetric results and applied to the entire sample. 

GSPaul

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[Jordan Mallon]

It's worth point out that the term 'record holder' is being used in two subtly different ways here, which will also affect the estimated body mass. The 15 tonne animal that Hone and I came up with is statistically derived, and represents the animal at the far-right tail of a normal distribution (0.00000004% of an assumed population of 2.5 billion animals, spread over multiple million years). It is, almost certainly, undiscoverable. You're using 'record holder' to refer to an animal that has been found in the present day, the total all-time population of which has not been sampled.

In any case, there's little sense in arguing about the size of something that cannot ultimately be verified, but it is fun to think about. Ultimately, my paper with Hone is just a glorified thought experiment.

Jordan