Tyrannosaurus speed estimates + neornithischian phalanx from Lower Cretaceous of South Korea (free pdfs)

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

Recent dino papers not yet mentioned:

Free pdf:

Adrian T. Boeye & Scott Swann (2024)
Calculating Muscular Driven Speed Estimates for Tyrannosaurus
bioRxiv 2024.06.13.596099  (preprint)
doi: https://doi.org/10.1101/2024.06.13.596099
https://www.biorxiv.org/content/10.1101/2024.06.13.596099v1


Top speed estimates of extinct dinosaurs have been of long-standing interest to gain better understanding of the animals’ lifestyle and ecology. Tyrannosaurus rex top speeds have been examined using a wide range of methods that draw on more traditional biomechanical formulas, computer simulations, and allometric equations based on mass. However, these calculations may be made more precise using input from contemporary research on anatomy and biomechanics that account for mass allometry and scaling. This study builds on existing studies in anatomy, biomechanical data, and established equations for locomotion to calculate a muscular driven range of top speed for several (n=4) specimens that had sufficient data to undertake this work. When properly refined with additional data on muscle mass allometry and scaling, several adult specimens of T. rex could confidently be placed in a range of top speed from 7.7 to 10.5 m/s, and possibly up to 10.7 m/s. Additionally, a younger specimen of T. rex was analyzed and found to have a higher top speed than the adult T. rex at 6.3 to 14.5 m/s. Although the estimated top speeds in this study are slower than some previous estimates, these results find some support for slow running gaits and reinforce interpretations of T. rex as an active and effective apex predator. Future work can build upon this study by investigating how muscular driven top speeds may affect ontogenetic niche partitioning and prey species regularly targeted by adult T. rex.

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Free pdf:

Sang-Yoon Lee, Yuong-Nam Lee & Seung-Ho Jung (2024)
A neornithischian phalanx from the Lower Cretaceous Tando beds of Ansan-si, Gyeonggi-do, South Korea
Journal of the Geological Society of Korea 60(2): 135-142 (in Korean)
DOI: https://doi.org/10.14770/jgsk.2024.010

Free pdf:
https://www.jgsk.or.kr/xml/40809/40809.pdf


A single pedal phalanx (II-1) was discovered in the Tando beds (Albian) of the Tando Basin, the coastal outcrop north of Tando harbor, Seongam-dong, Danwon-gu, Ansan City, in 2021. By comparing its size and morphology to the phalanges of Early Cretaceous Asian dinosaurs, it was determined to belong to basal neornithischians, most similar to Jeholosauridae. This fossil indicates that neoceratopsian Koreaceratops, basal neornithischians, and ornithopod dinosaurs coexisted in the Albian time.

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[Gregory Paul]

A basic problem with all such efforts is that these are simulations of a simulation, not the actual animals themselves, so whatever speeds the models generate low and high are speculative. 

What is needed is a time machine and a speed radar. Of course someone have to stand a hundred feet or so in front of a Tyrannosaurus and try to get it to chase them. Preferably a well trained runner in case the slower speed estimates prove as is likely to be errant. Any volunteers? 

The way to tell that giant avepods were faster than same sized proboscideans is that the first have flexed legs with long feet and toes on a highly flexible ankle that they can use to push off into a full suspended phase as part of a full run, while elephants have much straighter limbs and the foot is a short stump fixed nearly immobile on the ankle. No foot push off no suspended phase and top speed is a walk/run amble of ~15 mph. This configuration is so speed limiting that juvenile proboscideans cannot achieve a suspended phase (check out the scenes of the baby elephants at top speed in the John Wayne/John Ford flick Hatari!, they have no suspended phase and are no faster than the adults -- also has perhaps the best vid of a rhino in full gallop). It would be interested for someone to study the ontogeny of locomotion in elephants. 

About the post which I suspect is already in press. They call everything T. rex. Not cited is Longrich and Saitta which following work by Larson and others prove that Jane is not even a tyrannosaurid, it being a subadult nontyannosaurid basal eutyrannosaur with too many teeth, too prominent a dentary groove, and a growth curve that has nothing to do with that of actual juvenile Tyrannosaurus. Using Jane to restore the locomotion of Tyrannosaurus would be like using a subadult dwarf island Mammuthus to study the ontogeny of locomotion in Loxodonta. Is it not better to use actual juvenile Tyrannosaurus to examine its location during growth? It is interesting that that the femur and tibia of actual Tyrannosaurus Baby Bob are both about 700 mm long, unlike same sized Jane in which the tibia is about a quarter longer than the femur. So growing Tyrannosaurus may not have been adapted for the same kind of locomotion of the basal eutyrannosaurs (I'm not going to robotically label Jane Nanotyrannus because while it is not Tyrannosaurus it may well not be Nanotyrannus either). The post is using all three species of Tyrannosaurus while ignoring their notable differences in proportions and following the continuing automaton practice of calling everything T. rex never mind the differences between them. It's the old T. rex rut which is holding back science. 

Some specimens are assigned masses of 8.5 to 9.5 tonnes (not entirely sure about the data, I could not see a way to access the Supplement). Really? Two legged Tyrannosaurus got to the mass of rare world record quad bull elephants which are bulky herbivores? Rigorously produced skeletals show that pneumatic Sue, Stan and Scotty are all about the same size at about 7.5 tonnes, that even after the recent increase in specific gravity values by Asier Larramendi and myself in The Anatomical Record (which is not cited in the post). After gorging on the latest Triceratops or edmonosaur kill they would weigh 8-9 tonnes. Of course warm climate predators are always in lean and mean condition to enhance hunting success (you can see the lower edge of the thin latissimus dorsi muscle sheet on the flanks of lions (https://www.krugerpark.co.za/africa_lion.html).

Now why is it that so few cite Happ chapter in the 2008 Tyrannosaurus rex book that shows it was an active predator taking on Triceratops in head to head combat? 

GSPaul

[Mike Habib]

Sure, any model will have its limitations, and if the mass estimates are poor, then this will obviously call the results into question. 

However, I also don’t think we can simply assert that an adult Tyrannosaurus must have been faster than a modern elephant simply because of qualitative assessments of limb morphology. Such assertions require testing, and as imperfect as it may be, modeling is our best approach for this until we have time machines and volunteers as bait.

Did tyrannosaurs clearly have more running-adapted limbs than elephants? Yes. Does this mean they were faster runners/walkers than elephants at all age classes? Not so much. It is quite possible that subadult tyrants were good runners but “aged out” as their size and capacity for suspensory running declined. The adults might simply have high speed associated limb traits as carry overs of their youth. 

Cheers,

—Mike H.

Michael B. Habib, MS PhD
Director of Data Visualization
Adjunct Associate Professor of Medicine
UCLA Cardiac Arrhythmia Center
Division of Cardiology
Vatche and Tamar Manoukian Medical Building
100 Medical Plaza, Suite 660
Los Angeles, CA 90095
MBH...@mednet.ucla.edu

Research Associate, Dinosaur Institute
Los Angeles County Museum of Natural History
900 W Exposition Blvd. Los Angeles, 90007

biology...@gmail.com
+1 (443) 280-0181

On Jun 21, 2024, at 10:23 AM, 'Gregory Paul' via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com> wrote:



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[Jura]

Additionally, tyrannosaurs evolved from fleet-limbed coelurosaurs. Elephants did not. I suspect that a lot of what makes tyrannosaurs appear faster is just a holdover from a more agile ancestry.

Cheers,

Jason

[Gregory Paul]

Proboscideans great and small cannot achieve a full run because they lack the long, mobile foot needed to translate muscle power into locomotory thrust regardless of the power of those muscles. If a giant tyrannosaur had the same limb muscle power as an elephant of the same mass, it could have much better utilized the muscle power to achieve a greater stride length  suspended phase at the same stride frequency. And those tyrannosaurs had big hips, big tail bases, and big cnemial crests for lots of retractor muscle mass and leverage, unlike slow poke elephants (there is very little muscle on elephant shanks, unlike the avepod drumstick). Nor do we know the power output per unit mass of adult tyrannosaur muscles, they may have been specialized in some manner to maximize power, especially for ambush burst speed. Probably more elastic rebound in the flexed legs with long tendons in big tyrannosaurs. 

Anatomy is the most important factor. Anatomy is why elephants of all sizes cannot run, while other animals the same size as juvenile elephants can run many times faster, and flexed limbed rhinos with long mobile feet including bull white rhinos of 3 tonnes can achieve a full gallop no elephant can dream of. And rhinos are not specialized for speed with their short limbs (and even dinky legged hippos can achieve a very fast suspended phase trot (https://www.dreamstime.com/stock-photo-running-hippo-frightened-towards-safety-water-image59548754). But somehow Tyrannosaurus is supposed to be slower than that. The long, bird limbed big tyrannosaurs were much more adapted for speed than rhinos much less elephants and hippos. 

As Christiansen and I showed, ceratopsids were better adapted for running than rhinos -- longer legs relative to mass, and those huge pelves supporting enormous thigh muscles. Not surprising because ceratopsids had to flee huge predators, and those needed to be even faster. 

That Tyrannosaurs evolved and grew up from fast running predators is a reason the presume that they remained fast predators which is true of all predators. 

Simulations do not "test" what the anatomy indicates. That cannot be done, because of all the speculation and assumptions inherent to simulations which result in a model that is not, and cannot test, the performance of the real animal. There is no need to use simulations to "test" whether the rectigrade sauropods and stegosaurs could run or not, their limb anatomy leaves no practical doubt they could not. Giant avepods head long running legs, so they could run. Probably faster than rhinos. But there is no reliable way to test that. 

The idea that we should opt for the middle of broad +/- estimated speed ranges as the most probable is not logical. There is strong pressure on arch predators to be as fast as their form can get away with to run down victims, so the upper end should be taken as the most likely option. Same for prey animals that live in the same habitat. All sort of creatures achieve extreme performances that push the bio limits, from wee little migrating birds crossing enormous bodies of water, fliers weighing a good portion of a tonne (which I was the first to demonstrate not that I am bragging about that), birds flying as high as airliners, mammals diving to incredible depths on a single breath. It's a bionorm. But when it comes to giant avepods they be slow never mind all the speed adaptations they have. 

That the calculations are so sensitive to modest differences in body mass (9.5 tonnes is only a quarter higher than 7.5, yet produces very different speed estimates) is itself an issue. Both in casting doubt on the methodology, and in how can we estimate the speed of a given individual when we cannot measure its actual mass? 

As for actually recording the speed of a living Tyrannosaurus imperator, a modification. No need to have a person play the hapless victim. Not ethical for one thing. Use drones to track some Tyrannosaurus over long periods of time. Use the drones' scanning systems to record the dinosaurs's top speeds! And also to 3-D model the beasts so we can use actual volume to get the mass. Now all we need is time travel. 

There is a real way that could prove the issue. A very very long stride trackway of a running Tyrannosaurus. Maybe along an also fast speed Triceratops or Edmontosaurus. Not holding my breath on that. 

GSPaul

 

https://groups.google.com/d/msgid/DinosaurMailingGroup/136867F4-E058-44F0-9778-11D6213E127F%40gmail.com

.

[Mickey Mortimer]

To Paul's objection regarding Tyrannosaurus species and the identity of Jane, this comes sadly close to a David Peters-ism.  I would say it's agreed there are at least three levels to publication on dinosaurs (and more broadly perhaps most objects of study) - basic description, interpretation of facts, and summary of knowledge.  Peters jumps the gun all the time, ranting how some review of whale evolution (third level) doesn't use his heterodox theory of whale diphyly (second level), for example.  And in this case, both taxonomy/phylogeny and speed estimation are second level issues separate from each other in this paper where individual specimens are tested.  Thus Boeye and Swann shouldn't be expected to cite heterodox second level theories like Paul's, any more than a study on e.g. Haplocheirus ecology should cite the Lori paper for it not being an alvarezsaur.  Also Paul's use of "prove" for his studies is Petersian, especially when none of the relevant small specimens have had published descriptions.

To Jura's argument- elephants did ultimately evolve from fleet-limbed afrotherians similar to hyraxes and afrosoricidans, and in a very short time from cursoriality to graviportality (within the Paleocene, right?).  So I don't think that distinction exists.

Mickey Mortimer

[Gregory Paul]

Longrich and Saitta show that the bone ring based growth curve of Jane, as well as Petey, are far from being in accord with a growing Tyrannosaurus, and are instead that of subadults, and Cullen et al. found the same for Petey, and no one has shown otherwise. So that is the current standard literature paradigm, and Jane cannot be a juvenile Tyrannosaurs. And L&S point out J has too many teeth when actual juvenile Tyrannosaurus have the same number as the adults as is true of nearly all reptiles as shown by Brown et al. 2015 J Anatomy. And that J has a prominent lateral dentary groove absent in juvenile Tyrannosaurus dentaries. And so forth. It is J being a Tyrannosaurus that has become untenable according to the published data. It was Carr 2020 who made the radical proposal that growing Tyrannosaurus underwent a radical metamorphosis as do some fish to try to explain a supposed dramatic transformation in form during growth, which is not seen in Gorgosaurus or Tarbosaurus. Amniotes do not undergo metamorphosis (if anyone knows otherwise please let us know).

It is possible that B & S did not know of the L & S paper when they finished theirs' for publication. In any case the B&S paper is obsolete and is using specimens from different subfamilies to restore the functional performance of a taxonomic chimera. And there is Baby Bob indicating that young Tyrannosaurus had a tibia no longer than the femur. 

GSPaul

https://groups.google.com/d/msgid/DinosaurMailingGroup/c4d76243-f80f-4c97-8642-b3b3fa8d2856n%40googlegroups.com

.

[Mickey Mortimer]

Longrich and Saitta and such are the latest in a back and forth among experts, but the resolution isn't there.  It's not even about correctness, it's about the consensus.  And without the consensus behind you, not even the smoking guns you think you have should matter to someone doing an equal or higher level study.  Basically, it's not the responsibility of a researcher to evaluate conflicts outside their area of study, and the default is to fall back on the consensus.  Now you have meta reasons for why that consensus is itself biased (T. rex is culturally special, etc.), but that's even further outside the responsibility of someone trying to estimate an individual's speed.

But since Boeye and Swann estimated the speed for four tyrannosaur individuals, why would their paper be obsolete?  They find x specimen ran y fast regardless of whether it's T. rex or T. regina or whatever, and the factors they use don't depend on taxonomy or that fine of a level of phylogeny.  It would be different if they combined information from specimens, but from my skim of the paper I don't think that's the case.

Btw- from my experience scoring the lateral dentary groove character for the Lori matrix, it's not one you want to depend on.  Groove depth is something you can't objectively score without a cross section, and varies anteroposteriorly between nutrient foramina.  It's also heavily dependent on lighting to evaluate.

Mickey Mortimer

[Jura]

On Saturday, June 22, 2024 at 9:41:57 AM UTC-5 Mickey Mortimer wrote:

To Jura's argument- elephants did ultimately evolve from fleet-limbed afrotherians similar to hyraxes and afrosoricidans, and in a very short time from cursoriality to graviportality (within the Paleocene, right?).  So I don't think that distinction exists.

 

==========================================================================

Neither tenrecs, nor hyraxes can be considered fleet-limbed animals. Both groups show relatively stumpy limbs and are hardly renowned for their agility. The earliest proboscidean with limb information comes from taxa like the Eocene Numidotherium. By this time, a "low-speed', graviportal stance appears to have been established. Contrast that with coelurosaurs, which are generally characterized as a group of "agile hunters" based on hind limb proportions (e.g., Ornitholestes or Zuolong). Tyrannosauroidea is a wastebin, but even within that mess of taxa we see a bunch of animals with cursorial limbs long before we get to Tyrannosauridae. So yes, I would say that there is a very distinct difference in evolutionary paths here.

Jason

[Jura]

On Saturday, June 22, 2024 at 9:23:43 AM UTC-5 Gregory Paul wrote:

Anatomy is the most important factor. Anatomy is why elephants of all sizes cannot run, while other animals the same size as juvenile elephants can run many times faster, and flexed limbed rhinos with long mobile feet including bull white rhinos of 3 tonnes can achieve a full gallop no elephant can dream of. And rhinos are not specialized for speed with their short limbs (and even dinky legged hippos can achieve a very fast suspended phase trot (https://www.dreamstime.com/stock-photo-running-hippo-frightened-towards-safety-water-image59548754). But somehow Tyrannosaurus is supposed to be slower than that. The long, bird limbed big tyrannosaurs were much more adapted for speed than rhinos much less elephants and hippos. 

I agree that anatomy is an important factor here. It is our primary source of evidence for anything to do with dinosaurs. That said, anatomy alone does not reveal physiology. This is all the more true for fossils that rarely preserve enough skeleton. Bone placement is not the same in death as it is in life, and many important soft tissues (cartilaginous joint capsules, ligaments, musculature) have to be inferred via careful reconstruction. All of these things will affect inferences on speed and agility. One can't just look at the anatomy of Tyrannosaurus and say that it must have been fast because of its "bird-like" limbs. Tyrannosaurus didn't evolve in a vacuum. It descended from a line of leggy animals. That doesn't mean it was fast. Moving 500 kg is way different than moving 7500 kg.

This is where biomechanical modeling can step in and offer reasonable limits to what was possible. I certainly wouldn't accept any concrete numbers from a biomechanical model, but I would look at the range of feasibility from these models as a likely upper and lower limit for where the "true" value lies. 

To quote George Box: "Essentially, all models are wrong, but some are useful."

 

Simulations do not "test" what the anatomy indicates. That cannot be done, because of all the speculation and assumptions inherent to simulations which result in a model that is not, and cannot test, the performance of the real animal. There is no need to use simulations to "test" whether the rectigrade sauropods and stegosaurs could run or not, their limb anatomy leaves no practical doubt they could not. Giant avepods head long running legs, so they could run. Probably faster than rhinos. But there is no reliable way to test that.

One cannot rely on just the anatomy. Especially when 90% of that anatomy remains unknown / unknowable. We need to make inferences on muscle size and placement, along with joint angles and shapes. Just because a dinosaur looks fast or slow in a rigorous skeletal drawing, that doesn't make it so. Simulating the movement at different speeds, muscle angles, muscle sizes, and overall body mass reveals a lot of what was probable. It may not have been what actually happened, and there will always be room for improvement, but simulations like these allow a narrowing of the range of likely values to something closer to reality. That these same models can be tested on animals that we do know near 100% of the anatomy, offers a means of ground-truthing (i.e.., validating) any assumptions ahead of time. 

 

The idea that we should opt for the middle of broad +/- estimated speed ranges as the most probable is not logical. There is strong pressure on arch predators to be as fast as their form can get away with to run down victims, so the upper end should be taken as the most likely option. Same for prey animals that live in the same habitat. All sort of creatures achieve extreme performances that push the bio limits, from wee little migrating birds crossing enormous bodies of water, fliers weighing a good portion of a tonne (which I was the first to demonstrate not that I am bragging about that), birds flying as high as airliners, mammals diving to incredible depths on a single breath. It's a bionorm. But when it comes to giant avepods they be slow never mind all the speed adaptations they have. 

Animals rarely live at the extreme of their abilities (see: Irschick et al. 2005). Even prey that are running for their lives tend to leave more energy "in the tank" than one would expect. I would argue that middle of the road may be too liberal when looking at extinct animals, and that conservative values are the closest to what the data will support. This is different for extant animals because we at least have the capacity to know so much more. There are too many missing data in for an accurate reconstruction and simulation of a long-extinct animal, which means we should probably stick to values that hover closer to the data.

 

That the calculations are so sensitive to modest differences in body mass (9.5 tonnes is only a quarter higher than 7.5, yet produces very different speed estimates) is itself an issue. Both in casting doubt on the methodology, and in how can we estimate the speed of a given individual when we cannot measure its actual mass? 

A 2 tonne difference is a lot of extra mass. That will have a large effect on the physics of the animal. As anyone who lifts weights can attest, one eventually reaches a weight range where the addition of just 5 lbs becomes too much. A fast sprinting human has a limited body mass where acceleration works. Usain Bolt (94 kg) and Ronnie Coleman (130 kg) would not even be competitive on a race track, despite both humans having near identical anatomy. Coleman's 38% extra body mass would reduce his sprinting performance, as can be alluded to here:

https://youtu.be/hU8Pz2BFy6Q?si=pIhk_PNMV_KkmvPL&t=32

 

Jason

Reference:

Irschick, D.J., Herrel, A., Vanhooydonck, B., Huyghe, K., Van Damme, R. 2005. Locomotor Compensation Creates A Mismatch Between Laboratory and Field Estimats of Escape Speed in Lizards: A cautionary Tale for Performance-to-Fitness_Studies. Evolution, 59(7), 1579-1587.

[Gregory Paul]

The situation with Jane does not impact the speed estimates for adult Tyrannosaurus. Using Jane to restore the ontogeny of speed performance in the genus is spurious. Unfortunately we do not have an actual juvenile Tyrannosaurus complete enough to work with, Baby Bob being very partial. 

It is incumbent for authors to be familiar with the ongoing situation and inform their readers about it. As it is B & S leave readers with the impression that Jane is a juvie Tyrannosaurus that can be used to reliably restore the ontogeny of the locomotion of the taxon. They could have noted the dispute by citing L & S,  and presented the paper as a possible locomotory ontogeny, or a comparison between a small gracile basal eutyrannosaur and the megatyrannosaurid of the same habitat. As I noted price it looks like actual juv Tyrannosaurus do not have lower legs as long as those of the basal eutywrannosaurs. 

I just looked and it may be that Bloody Mary which is no way the same genus as Jane or Nano may have a tibia/femur ratio intermediate to Baby Bob and Jane. If so interesting, very interesting. 

I did a deep look into the lateral dentary groove issue. Specimens assignable as juv Tyrannosaurus for assorted reasons always have very little if any groove, like their parents. Almost all the lithe basal eutyrannosaurs have a very prominent groove very unlike any Tyrannosaurus, but like Gorgos of all ages - Tarbos are more like Tyrannos, except the smallest two juvenile skulls (including Raptorex) have a short but distinct groove). The exception is Stygivenator molnari that lacks a groove. This is but one reason that even though it is closest to Bloody Mary in overall form, it cannot be the same taxon at least at the species level. 

GSPaul 

https://groups.google.com/d/msgid/DinosaurMailingGroup/a2a6d573-ba0b-4736-8512-5453f232c3b7n%40googlegroups.com

.

[Mike Habib]

Anatomy is a lynchpin of all hypothesis building and testing for the mechanics of extinct animals - on this I think we can all agree. It forms the basis for our questions, the assertions we wish to test, and the data that we feed into models. It is also a source of validation for models of extinct organisms - good models make predictions about anatomy that we can then check.

But the mechanics ultimately represent the interaction between that anatomy and the physics. Which means it is insufficient to merely assert from anatomy - we must also do the math. If you have the math to show that a large tyrannosaur could run fast with a suspensory phase, then show the work - that would be a convincing argument.

The thing is, I think you *do* have the math - despite your dismissive language about quantitative methods. Your mass estimation model (yes, it counts as a form of modeling) is rather good and has some validation to back it up. Your lighter masses, fed into the model in discussion, produces fairly brisk speeds. So, in fact, your hypothesis seems to hold up pretty well. 

Some more specific thoughts below…

“If a giant tyrannosaur had the same limb muscle power as an elephant of the same mass, it could have much better utilized the muscle power to achieve a greater stride length suspended phase at the same stride frequency.”

This is a very fine hypothesis. It is one that the paper in question set out to test. Their conclusion was that it fails their test. Why? Because they predict that the ability of the long-limbed, digitigrade morphology to translate muscle power to high Froude number locomotor impulses at the ground declines with large size. They might be wrong, but they aren’t *automatically* wrong just because their results don’t match expectations (and as noted above and below, I’m not actually sure they disagree that much. It seems to hinge on mass).

“That Tyrannosaurs evolved and grew up from fast running predators is a reason the presume that they remained fast predators which is true of all predators.”

Um… no. No, we cannot presume that ontogenetic and phylogenetic speed reductions never happen. First of all, they do in some living lineages. But more importantly, large living predators are mostly mammals a fraction of the size of a large tyrant - not closely comparable phylogenetically nor ontogentically.

“Simulations do not "test" what the anatomy indicates. That cannot be done, because of all the speculation and assumptions inherent to simulations which result in a model that is not, and cannot test, the performance of the real animal. There is no need to use simulations to "test" whether the rectigrade sauropods and stegosaurs could run or not, their limb anatomy leaves no practical doubt they could not.”

Yes, yes they do. That’s the whole point of a model. They test the anatomical predictions. You may not think that the tests are very good for one reason or the other, and that’s fine. However, if you posit that there’s too much uncertainty to test the hypotheses from anatomy in any way whatsoever, then the answer must remain “unknowable”. We can *never* get away with “this doesn’t have to be tested”. Not in the sciences.

Keep in mind that even something like the limb positions in a sauropod is, at some level, a form of modeling. And the ability of those positions to support weight etc are also modeling exercises. 

Now, you do make a solid point that validation is critical. We need some way of checking if the model is working. There are a few ways of doing this, but a depressing number of models don’t do so. And in those cases, skepticism is warranted.

“All sort of creatures achieve extreme performances that push the bio limits, from wee little migrating birds crossing enormous bodies of water, fliers weighing a good portion of a tonne (which I was the first to demonstrate not that I am bragging about that), birds flying as high as airliners, mammals diving to incredible depths on a single breath. It's a bionorm. But when it comes to giant avepods they be slow never mind all the speed adaptations they have.”

Yes, but those extreme performance examples are all predictable from the relevant bodies of math. Pennycuick’s “burning the engine” model explains long range flight, my launch and burst locomotion models explains large fliers, respiratory physics and exchange rate maths explain the flight ceilings, and so forth. The issue with giant avepods is that we don’t know if the apparent adaptations to speed are the result of phylogenetic inertia, ontogenetic carryover, or actual selection on adult speed. 

*Something* in there is fast - on that you’re almost certainly correct. It could be the ancestors, the kids, the adults, or all of the above. Telling these apart requires some leg work (ha) beyond just punting from our instincts.

“That the calculations are so sensitive to modest differences in body mass (9.5 tonnes is only a quarter higher than 7.5, yet produces very different speed estimates) is itself an issue. Both in casting doubt on the methodology, and in how can we estimate the speed of a given individual when we cannot measure its actual mass?”

Now this is a salient observation - but I read it a little differently from how you do. I don’t think it calls the *methods* into question. Rather, it changes the conclusion. The *actual* result of the paper is not “Tyrannosaurus was slow.” The true result is “if Tyrannosaurus was 7.5 tonnes the it was pretty fast. If it was 9.5 tonnes then it was slow.” Based on their model, at even less than 7.5 tonnes, it might be very fast, indeed. So, at some level, what it really says is that mass estimation is the key here. And on that front, your mass estimate model does seem quite good, and so I’m personally inclined to lean towards “light and fast” on this one. 

Cheers,

—Mike H.

Michael B. Habib, MS PhD
Director of Data Visualization
Adjunct Associate Professor of Medicine
UCLA Cardiac Arrhythmia Center
Division of Cardiology
Vatche and Tamar Manoukian Medical Building
100 Medical Plaza, Suite 660
Los Angeles, CA 90095
MBH...@mednet.ucla.edu

Research Associate, Dinosaur Institute
Los Angeles County Museum of Natural History
900 W Exposition Blvd. Los Angeles, 90007

biology...@gmail.com
+1 (443) 280-0181

On Jun 22, 2024, at 7:23 AM, 'Gregory Paul' via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com> wrote:



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[Russell Engelman]

Jura is completely right. The digitigrade posture of tyrannosaurs is more likely related to holdovers from cursorial ancestors rather than reflecting cursorial habits. IIRC, I once explicitly saw one author (I want to say Prothero? But I can't find it offhand) describe this same phenomenon with regards to Paraceratherium: Paraceratherium is digitigrade because its whole group (Rhinocerotoidea) is digitigrade, and it inherited it from its ancestors, not because this animal was cursorial in any way. Same with modern rhinos and hippos, to a degree. Elephants were never cursorial. Even the earliest ones seem to have been graviportal, in a manner analogous to Paleocene pantodonts or condylarths, and they evolved that way from what were likely small, generalized, ambilatory, and plantigrade ancestors, based on other afrotherians. This makes their limbs distinctly weird among mammals (even the other surviving megafauna) because they never had leftover bits from fast moving ancestors and their post K-Pg history was basically "all graviportality, all the time".

[Andreas Johansson]

If 9.5 tonnes v. 7.5 tonnes makes a big difference to speed, maybe the question “of fast was Tyrannosaurus” is limitedly meaningful, because it may have differed a lot from one healthy adult to another. 

Or not, if 9.5 is outside the actual weight range and the relationship is nonlinear enough that the difference between 7.5 t and 5.5 t is much less. But 9.5 is just 27% more than 7.5, and whether it was attained or not it’d be weird if the relative size range was narrower than that. 

—
Andreas Johansson

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[Gregory Paul]

And rhinos and hippos can achieve high speed gallops and/or trots.

GSPaul

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[Gregory Paul]

Animals don't push the limits? 

Sperm whales are high metabolic rate arch predators that in order to hunt deep sea squid can dive thousands of feet and chase down and chow down on their prey on a single breath and not get the bends while doing so. 

If they were known from fossils only, then little doubt simulations would never show that, and any who claimed otherwise would be dismissed as extremists wandering outside well founded biological boundaries. 

Much the same for elephant seals. 

Would simulations show birds cruising as high as jetliners if they were just fossils? No. And those who might dare argue they could would be waved away by the digital establishment. 

I recall back in the olden times when it was calculated that super pterosaurs had to weigh no more than humans to get into the air. I went along with that - seemed to make sense -- until doing the necessary function of restoring their anatomy and realized azhdarchids weighed a few hundred kilograms. And they have full wings, so animals approaching moa masses could fly. Duh.  I was told don't be silly. I noted that gliders with the same wing span/area to mass fly to the super pterosaurs could too. Duh. Simulations confirming the fact are nice, but they are not critical, and if they showed otherwise they would be wrong because anatomy trumps inherently speculative simulations. 

Pterosaurs are quadrupedal like bats on the ground, and the arms are much more powerful than the legs in both, and bats take off on all fours. Unlike birds which cannot push off with their arms and use powerful legs if they have them. So pterosaurs should have been more prone to arm pushing to taking off than birds, although they may have done take off runs under certain circumstances they being stronger legged than bats, or maybe they didn't. Simulations are useful, but not critical, and if they indicated otherwise more likely there is a problem with the modeling, and it would not discredit arm dominant take offs in pterosaurs. 

As I said back in PDW, it's the anatomy. That the arch predatory Tyrannosaurus with massive muscled, bird like limbs with long mobile feet that was chasing down rhino legged ceratopsids was anywhere near as slow as herbivorous, stump footed elephants that don't need to run away from anything is so contrary to basic evolutionary selective pressures that running Tyrannosaurus is automatically the superior hypothesis, and cannot be refuted anymore than could establishing extinct sperm whales as being only shallow divers by complex computer simulations as  the latter certainly would claim, having inaccurate parameters unavoidably fed into them. 

He-man Ronnie Coleman is drastically different from gracile Usain Bolt in body form. And probably muscle fiber composition. Athletic trainers are good at spotting those differences and directing people to what their body type is best suited for. 

GSPaul

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[Thomas Richard Holtz]

BTW, if a presentation from last year's SVP meeting makes it through the peer review process with the conclusions the same, the present bioRxiv preprint people are talking about here will be moot.

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Thomas R. Holtz, Jr.
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[Mike Habib]

We don’t know whether models might have predicted deep diving in sperm whales or high altitude flight in birds, if we didn’t live alongside those animals. It’s an interesting hypothetical. After all, we have models that predict deep diving in some fossil reptiles and high altitude flight ability in some pterosaurs. But then, we also have modern exemplars to inform and validate those models.

That said, no one is claiming that models are perfect, or that there aren’t numerous things that we cannot effectively model in fossil animals. That’s not the point anyone is trying to make.

The point is that tests of hypotheses based on anatomical observations *are the whole game*. They’re not merely “nice”. And yes, as much as you may hate it, they’re critical. That test need not always be a model - but for the physics of locomotion, it’s usually the best we got.

So. You want to make a compelling case? You want to actually test hypotheses of animal performance in the fossil record? Then do the math. Do the math. Do the math. If you can’t show us the math, we have no reason to accept your assertion. Show us the math. Preferably, math that can be shown to get the right answer with extant systems.

There is no “digital establishment” unfairly shooting down beautiful ecological hypotheses. In fact, a lot of the most powerful models are not even digital. I worked up my original unified launch theory equations on graph paper and a white board. 

To say that if a model rejects your favored hypothesis then it is clearly wrong is the antithesis of scientific methodology. It’s fine if you think the method is flawed. It’s even better if you can provide a better model that gets a different result. Getting things wrong and then working to get better is a core part of doing good science. Nothing is ever “automatically the superior hypothesis”. 

Incidentally, the ecological narrative of giant tyrannosaurs chasing down large ceratopsians, both moving at high speed, makes more (not fewer) assumptions than a first principles approach to tyrannosaur speed estimation. 

Don’t get me wrong. It’s a wonderful idea and might be spot on. But if you want to convince me - then do the math. I’ll bet you can. Frankly, I think you’re giving yourself too little credit for being able to do quantitative work. After all, your skeletal volume to mass estimation method is a very elegant model.

Cheers,

—Mike H.

Michael B. Habib, MS PhD
Director of Data Visualization
Adjunct Associate Professor of Medicine
UCLA Cardiac Arrhythmia Center
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MBH...@mednet.ucla.edu

Research Associate, Dinosaur Institute
Los Angeles County Museum of Natural History
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On Jun 23, 2024, at 8:03 AM, 'Gregory Paul' via Dinosaur Mailing Group <DinosaurMa...@googlegroups.com> wrote:



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