Tyrannosaurus Running Brought into Question

[Loon]

Investigating the running abilities of Tyrannosaurus rex using stress-constrained multibody dynamic analysis

Here's the article from Science Alert:
https://www.sciencealert.com/running-would-have-broken-an-adult-tyrannosaurus-rex-s-legs
It suffers from a bit of "Dinosaurs are ruined!"

Here's the article at PeerJ:
https://doi.org/10.7717/peerj.3420
Thankfully it's open access.

[stargatedalek]

It does make a lot of sense if it didn't run, most of the available prey wouldn't have. It also explains why the juveniles would be so extremely specialized as they are.

[Simon]

In other news, the world is still round, and Generalissimo Francisco Franco is still dead.

I am almost tempted to call this study a form of paleontological "click-bait".  Let's sum up what's been pretty well acknowledged for quite a few years now:

1.  Adult TRexes couldn't run (though obviously they could "fast walk" quickly enough to catch their prey), and

2.  Juvenile TRexes were probably "hell on wheels", COULD run and filled in a couple of intermediary niches in the ecosystem as a result.

So, the following quote from the article is really not news.  I think it pretty much restates the widely accepted view.  Nothing new here except the way they do the calculations (which isn't definitive in any event):

"The fact that T. rex was restricted to walking also supports arguments of a less athletic lifestyle. This means the results could change the way we view the effects of how the size and shape of T. rex and other large bipedal dinosaurs alters as they grow. Previous studies have suggested the torso became longer and heavier whereas the limbs became proportionately shorter and lighter as T. rex grew. These changes would mean that the running abilities of T. rex would also change as the animal grew with adults likely to be less agile than younger individuals"

[CityRaptor]

Nothing new. And in a few months or so, there will be a study contradicting this one. That is how it usually goes.

"Science ruins dinosaurs again."
Needs lots of grunting, shouting and exclamation marks.

[suspsy]

Tom Holtz says there's an article coming out soon listing a ton of problems with this study.

[CityRaptor]

See? That is what I'm talking about.

That's the thing with palaeontology, there are often no absolutes.

[Jose S.M.]

Even if this was accurate and true, I still think it would outrun me 

[Neosodon]

How fast adult T. rex was is relative to it's prey. It could most certainly outrun ankylosaurs and saurapods. I highly doubt it could outrun most ornithomimasaurs. I think it could probably outrun any ceratopsian. But  the biggest grey area is hadrosaurs. They should also do a study of hadrosaurs and see how fast T. rex would need to be to catch one of its major food sources.

[Huskies]

I wonder what parameters that they used for this analysis including the muscle size, muscle attachments, and the animal locomotion considering we don't have any living animal that resemble t-rex. The closes we have are birds but they don't have tail like theropod dinosaurs. I don't even think we have clear idea how heavy t-rexes were. Do we even know how fast triceratops and duckbill dinosaurs were? As indicated, the speed of the predator is related to the speed of the prey. I still think that t-rex was able to run. There was an article in Paleoking blogspot  that talk about t-rex 's speed that I found it interesting.

[The Atroxious]

I wonder what parameters that they used for this analysis including the muscle size, muscle attachments, and the animal locomotion considering we don't have any living animal that resemble t-rex. The closes we have are birds but they don't have tail like theropod dinosaurs. I don't even think we have clear idea how heavy t-rexes were. Do we even know how fast triceratops and duckbill dinosaurs were? As indicated, the speed of the predator is related to the speed of the prey. I still think that t-rex was able to run. There was an article in Paleoking blogspot  that talk about t-rex 's speed that I found it interesting.

I can already see problems with the muscle attachment points, or lack thereof, concerning the sartorius and tensor fasciae latae in particular. The iliac crest is suspiciously bare in the attached image.

I'm really not convinced of the argument this article presents. I find myself suspicious of most of the claims that any given large theropod couldn't run, since most of them don't account for the full musculature of the legs and pelvic region, and many will also oversimplify the reasoning behind the claim.

[ZoPteryx]

I too am slightly skeptical.  My main concern is that I don't think we know enough about how much Tyrannosaurus weighed; the upper estimate is nearly double the lower!  Sure, the maths don't lie, but they can be led astray.

Worth noting is that another recently published paper independently came to the same conclusion about Tyrannosaurus, though it wasn't the main objective of the paper.  This was the result of scaling models based on extant animals, for which the method proved quite accurate.

https://www.nature.com/articles/s41559-017-0241-4

[suspsy]

Okay, here are Thomas Holtz's thoughts, posted on his FB page:

People have been asking for my comments on the recent PeerJ paper by Sellers et al. on Tyrannosaurus rex running ability (https://peerj.com/articles/3420/). I figured I would do one single long post rather than respond to the individual threads.

Methods: Their methods (integrating two separate biomechanical approaches) points to the way that future such studies should go. With increasing computational power, we can begin to bring together multiple lines of evidence simultaneously and in concert. As they note themselves even this complex study is simplified from the natural system: for instance, they did not attempt to model the action of the foot with the substrate in a non-linear fashion. But that is Science for you: it works iteratively.

(I imagine that future studies will help address additional issues such as complient soft tissues in the system; the role of stress distribution in the rest of the body; and so on.)

So the numbers they produce are not unrealistic by any means. And they are fairly precise (have fairly small error bars). But are they accurate? That is, does their model reflect the actual performance of the living, breathing animal?

Confidence in the analysis: To go straight to the most important aspect of the study: what confidence do we have that the analytical methods accurately reflect the abilities of a particular extinct animal? The authors have done a remarkable job of integrating separate techniques for a computer simulation of a particular individual of an extinct species. However, it is difficult to judge is said simulation can be expected to produce realistic values in a biological system.

We would have much greater confidence in this analysis if it were initially done on extant animals for which we can more accurately and independently assess their locomotory performance values, and thus see to what degree this novel method recovers meaningful results. As it stands, this is apparently the first such application of this technique, and it is applied to an animal at the extreme end of the size range of terrestrial bipeds. This is not to say that their results are incorrect: rather, that we are extremely limited in our ability to test whether their results are correct.

Had this paper been part II of a two-phase program—the first part of which would be simulations on extant animals of various sizes to see if the method recovers realistic values—would make our confidence in their conclusions far stronger.

And their conclusions are limited to a particular case: looking at a single (presumably typical) individual of a single species at a single growth stage. Which is fine: we have to start somewhere! But their introduction, discussion, and conclusions try to stretch beyond this.

Adults are not the only functional stage, and adaptations are not always acquired at the species level: After all, juvenile and subadult Tyrannosaurus rex are perfectly important growth stages as well, and indeed the animals had to operate at these growth stages in order to achieve the adult status.

Which gets to the more significant point: the particular adaptations in question (elongation of the hind limb and associated pelvic and caudal transformations) need not be adaptations for the adult form in order to be the product of selection for increased cursoriality. It might well be that selection favored these cursorial-like features for the smaller body size, and were simply carried along into the adult form. (To be fair, nearly all the papers cited by these authors are also interested almost solely in adult forms, and this is obviously a subject of broad public interest. Furthermore, this would in no way invalidate the present study. But it should be recognized that the features of concern may not have been of special import to the full adult.)

Related to this, the adaptations in question in Tyrannosaurus rex are by no means special to that species. The transformation of the limbs, pelvis, and caudal anatomy (and their inferred soft-tissue correlates) all arose elsewhere in phylogenetic history: around the base of Tyrannosauridae and its immediate outgroups (that is, including Appalachiosaurus, Alectrosaurus, Bistahieversor, and related taxa). Again, this does in any way invalidate the results of the study, but it might make the conclusions somewhat misleading. That is, the adaptations in question may indeed have been selected for increased cursorial ability, but in earlier, smaller, more basal members of the tyrant dinosaur clade: their presence in Tyrannosaurus rex would thus be an evolutionary left over. And thus to argue about the significance of these adaptations without a phylogenetic context would be comparable to doing a biomechanical study of the human hand arguing that its pentadactyl condition is related to our grasping ability (rather than simply our evolutionary heritage as tetrapods).

Of relevance to this, there is a significant paper not cited in the present study finds a 4.5-8.0 km/h speed for a Lancian tyrannosaurid (either a sub-adult Tyrannosaurus rex or a Nanotyrannus [assuming these are indeed separate things]):

Smith, S.D., W.S. Persons IV & L. Xing. 2016. A tyrannosaur trackway at Glenrock, Lance Formation (Maastrichtian), Wyoming. Cretaceous Research 61: 1-4.DOI: 10.1016/j.cretres.2015.12.020

Conflation of the idea of "high-speed pursuit" and relatively higher speeds: The authors do note the distinction between previous studies who proposed absolutely high running speeds for Tyrannosaurus rex and those who only suggested relatively high speeds (when compared to other dinosaurs). The present analysis does seem to reject the former, but has no bearing on the latter until such time as comparable analyses on done on ecologically-relevant taxa (in particular, potential prey species). It may be that these other forms are found to be significantly slower than T. rex, and this ecologically the adaptations of Tyrannosaurus would still be relevant as "speed" adaptations for the environment in which it lived.

[BlueKrono]

Would the biomechanics of large, bipedal birds like ostriches and emus be useful in understanding those of theropod dinosaurs?

[Halichoeres]

Would the biomechanics of large, bipedal birds like ostriches and emus be useful in understanding those of theropod dinosaurs?

Some of them, but it's hard to scale it up because the loadings would have to change so drastically on increasing the length of each bone. Beyond the straightforward fact that mass increases as the cube of length, holding everything else equal, the fact that our biggest birds are descended from flying ancestors means they're probably carrying around design features that constrain them in ways that wouldn't affect something like Tyrannosaurus.

[Huskies]

Would the biomechanics of large, bipedal birds like ostriches and emus be useful in understanding those of theropod dinosaurs?

The problem is they don't have tail like theropod dinosaurs. If you look at crocodiles and reptiles, that have muscles in their tail that help them move. I believe theropod dinosaurs also have those, too. If you look at crocodile and komodo dragon skeletons, they don't seem to be able to run, yet they are able to run fast if they have to. I have seen them run in real life and they can move fast if they have to.
We also don't know t-rex hunting strategies. Did t-rex ambush their prey, outrun their prey, or hunted like wild dogs in Africa where they have better stamina than their prey?
Just looking at the skeleton can be misleading. Look at lion and tiger skeleton. Their skeletons are very similar but their hunting strategy and lifestyle are very different.