Tyrannosaurus birdlike foot function + Coelophysis jumping performance (free pdfs)

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

New papers:

Free pdf:

Adrian Tussel Boeye, Kyle Logan Atkins-Weltman, J. Logan King & Scott Swann† (2026)
Evidence of bird-like foot function in Tyrannosaurus
Royal Society Open Science 13(2): 252139 .
doi: https://doi.org/10.1098/rsos.252139
https://royalsocietypublishing.org/rsos/article/13/2/252139/480521/Evidence-of-bird-like-foot-function-in


The movement of extinct animals has been of long-standing interest, with Tyrannosaurus rex being a locus for this fascination. Foot-fall kinematics within T. rex and their effect on stride length (SL) and locomotion have yet to be investigated thoroughly, despite their impacts on the potential speed of T. rex. Here, we present novel findings on the function of the foot of T. rex, using three predictive allometry-based equations and several statistical tests including Kruskal–Wallis tests to reveal a complex and bird-like function of the foot. This includes a very bird-like gait defined by higher stride frequencies, proportionally short SLs and elevated speeds. Comparisons between the four sampled specimens of T. rex with extant bipedal species are more akin to the gaits of the ground-truth modelled Struthio camelus and are notably divergent from the modelled Homo sapiens. Additionally, our models are consistent with recent studies suggesting slower to more intermediate top speeds for adult Tyrannosaurus that fall within the range of 5–11 m s−1. This study lays the groundwork for future studies to add comparisons with additional theropods and potentially identify ecological differences between species.

News:

https://www.nytimes.com/2026/02/24/science/tyrannosaurus-rex-tiptoes-dinosaurs.html

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Free pdf:

James P. Charles, Delyle T. Polet & John R. Hutchinson (2026)
Form–function relationships determining optimal jumping performance in an early bipedal dinosaur
Journal of the Royal Society Interface 23(235): 20250918
doi: https://doi.org/10.1098/rsif.2025.0918
https://royalsocietypublishing.org/rsif/article/23/235/20250918/480511/Form-function-relationships-determining-optimal


Elucidating the optimal movements of extinct animals is crucial for understanding the mechanisms behind evolutionary advantages and adaptations. Here, the vertical jumping performance of the Late Triassic theropod dinosaur Coelophysis bauri is predicted using optimal control simulations and compared with that of the extant generalized bird Eudromia elegans. These simulations predicted similar jumping performances between these species, reflective of their geometrically similar hindlimbs. However, differences in overall body shape and size led to different mechanisms by which these jumps were achieved. The jumping performance of Coelophysis was found to be highly sensitive to changes in the range of motion allowed at the proximal tail joint, and changing the relative mass of the tail also revealed how archosaurs with similar body plans but relatively heavier tails would benefit more from this increased range of motion in terms of jumping performance than those with lighter tails. This study provides important insights into how body size, morphology and joint dynamics may have impacted the ability to jump within morphologically diverse bipedal archosaurs, and thus informs possible hypotheses regarding the evolution of jumping and other high-demand movements within Archosauria.

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[Gregory Paul]

A new podcast on Tyrannosaurus (https://www.youtube.com/watch?v=J8HZctRq-o4) was so inaccurate and downright deceptive about the dimensions and volumes of my profile-skeletals that I have posted a reply at https://gspaulscienceofnonreligion.substack.com/p/the-science-of-dinosaurs-tyrannosaurus. It addresses issues of the ethics of podcasts posted anonymously, they should be considered borderline ethical at best. 

GSPaul

 

[mkir...@gmail.com]

Greg, you could report the video for copyright infringement.  

[Gregory Paul]

I'm actually not sure the image used is outside of free use for such purposes, it having appeared in a couple of technical papers. What bugs me is that it was misused in association with the absurd claim that I used scale bars in published figures for the restorations, when of course I used reliable bone measurements, etc. And the podcaster (whose name I have figured out) did not do the courtesy and scientific necessity of using the scale bar in the figure to check the bone measurements. Had he done so he would have had to deal with the skeletals and their volime estimates being accurate. Now that would have been an interesting podcast, and he is free to retract and revise his claims. 

GSPaul

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[The Dinosaur Heretic]

Isaac is on the DMG and has engaged in conversation a number of times. I’m sure if you sent him an email, he could explain his thought process. He’s quite a kind person.

Cheers.

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[Gregory Paul]

He is more than free to do so. 

GSPaul

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[Gregory Paul]

Hi guys. Although I don’t think speed restorations are all that useful, I got to thinking about the new paper and checked to see what mass they have Tyrannosaurus at. Way too high for Sue, and it is easy to see why as per the attached comparison to my accurately proportioned profile skeletal (don't spread the image around publicly). So yet another post on the subject of Tyranno size just after the other one (https://gspaulscienceofnonreligion.substack.com/p/the-science-of-dinosaurs-yet-more). 

My correcting the errant paleo masses job is endless.  

 

GSPaul

 

[Chaos Soahc]

After reading the Coelophysis paper above, I may be mistaken and completely misinterpreting the paper, but the paper states that their coelophysis model jumped over a meter vertically, but isn't coelophysis around 1 meter tall at the hip anyway? Do they mean they can jump a meter taller than their hip height?

- Alex.M

[Sean McKelvey]

> After reading the Coelophysis paper above, I may be mistaken and completely misinterpreting the paper, but the paper states that their coelophysis model jumped over a meter vertically, but isn't coelophysis around 1 meter tall at the hip anyway? Do they mean they can jump a meter taller than their hip height?

I'm fairly sure they mean it could jump 1m off the ground? so Coelophysis could jump it's own hip height off the substrate.

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[John Hutchinson]

Thank you for the interest. Our study's simulations were "maximizing CoM height (substrate to peak height)". So, basically how much the centre of mass is raised (maximized vertical CoM height). And similar to height above hip height, since CoM is near hips. If you look at the supplementary videos, this is clearer.

-John Hutchinson

On Thu, 26 Feb 2026 at 23:43, Sean McKelvey <smc...@gmail.com> wrote:

> After reading the Coelophysis paper above, I may be mistaken and completely misinterpreting the paper, but the paper states that their coelophysis model jumped over a meter vertically, but isn't coelophysis around 1 meter tall at the hip anyway? Do they mean they can jump a meter taller than their hip height?

I'm fairly sure they mean it could jump 1m off the ground? so Coelophysis could jump it's own hip height off the substrate.

On Fri, 27 Feb 2026 at 08:22, Chaos Soahc <soahcc...@gmail.com> wrote:

After reading the Coelophysis paper above, I may be mistaken and completely misinterpreting the paper, but the paper states that their coelophysis model jumped over a meter vertically, but isn't coelophysis around 1 meter tall at the hip anyway? Do they mean they can jump a meter taller than their hip height?

- Alex.M

On Wednesday, February 25, 2026 at 7:47:57 PM UTC-8 Gregory Paul wrote:

Hi guys. Although I don’t think speed restorations are all that useful, I got to thinking about the new paper and checked to see what mass they have Tyrannosaurus at. Way too high for Sue, and it is easy to see why as per the attached comparison to my accurately proportioned profile skeletal (don't spread the image around publicly). So yet another post on the subject of Tyranno size just after the other one (https://gspaulscienceofnonreligion.substack.com/p/the-science-of-dinosaurs-yet-more). 

My correcting the errant paleo masses job is endless.  

 

GSPaul

 

Adrian Tussel Boeye, Kyle Logan Atkins-Weltman, J. Logan King & Scott Swann† (2026)
Evidence of bird-like foot function in Tyrannosaurus
Royal Society Open Science 13(2): 252139 .
doi: https://doi.org/10.1098/rsos.252139
https://royalsocietypublishing.org/rsos/article/13/2/252139/480521/Evidence-of-bird-like-foot-function-in


The movement of extinct animals has been of long-standing interest, with Tyrannosaurus rex being a locus for this fascination. Foot-fall kinematics within T. rex and their effect on stride length (SL) and locomotion have yet to be investigated thoroughly, despite their impacts on the potential speed of T. rex. Here, we present novel findings on the function of the foot of T. rex, using three predictive allometry-based equations and several statistical tests including Kruskal–Wallis tests to reveal a complex and bird-like function of the foot. This includes a very bird-like gait defined by higher stride frequencies, proportionally short SLs and elevated speeds. Comparisons between the four sampled specimens of T. rex with extant bipedal species are more akin to the gaits of the ground-truth modelled Struthio camelus and are notably divergent from the modelled Homo sapiens. Additionally, our models are consistent with recent studies suggesting slower to more intermediate top speeds for adult Tyrannosaurus that fall within the range of 5–11 m s−1. This study lays the groundwork for future studies to add comparisons with additional theropods and potentially identify ecological differences between species.

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[Chaos Soahc]

so if i am understanding this, if for example the standing CoM Height was 0.60 meters, the Coelophysis would be jumping a meter above this height? or would it only jump 0.45 meters to reach 1.05 meters?

[John Hutchinson]

The latter. In the paper's nominal simulation, 1.06 m height was obtained from a 0.43 standing hip height; i.e. a net increase of 0.63 m.

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[Chaos Soahc]

Alright, thank you for helping me understand, could it possibly jump higher than this? Not that it isn't impressive, thats 2 times it's CoM height, and also, I just watched the video, its much more clearer now, thought isn't the hip height still a bit taller than the CoM height? aren't there larger individuals of Coelophysis, I was under the impression they were a bit bigger than this?

[John Hutchinson]

The paper simulates maximal height jumping, so under the assumptions made that's the best possible. Hip height is slightly above CoM height, yes. There surely are somewhat larger Coelophysis, but not in a game-changing way, and our study didn't try to encompass populational variation.

--John H

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