Giant dinosaur speed discussion thread

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Oh, and yes, I was referring to Sellers et al. 2013, sorry for not answering that query earlier.

For reference, in Christiansen (2000), AMNH 5027's femur had strength indicator values of 12.3, the tibia 7.5, and the fibula 0.5 (I don't consider the other Tyrannosaurus specimen because Christiansen notes that it had slightly distorted diaphyses, giving it significantly lower strength indicator values). A 3.5 tonne Asian elephant's values were 12 units for the humerus, 12.7 for the femur, 9.0 for the tibia, and 0.7 for the fibula. A 6.2 tonne African elephant had values of 12.6 for the humerus, 10 for the femur, 7 for the tibia, and 0.9 for the fibula.

I should note, though, that these weren't the only times someone ever tried to see how strong the limb shafts of giant dinosaurs were (and in the case of Tyrannosaurus and other predators, the results were actually different below). Bakker says this in The Dinosaur Heresies.

A quite different approach to the question of dinosaur speed is provided by calculating the maximum strength of the bone shafts of the limbs. Legs do break in nature, and evolution usually outfits a species with bone shafts strong enough to withstand the highest strains imposed when muscles contract. Rhinos have relatively stout, thick-shafted legs. Elephants feature a more spindly design. To measure the shaft strength of dinosaur limbs, I constructed scale models in clay of the life appearance of various species. I then calculated the live weight by measuring the volume of the model (most land animals are a little less dense than water, so live weight is about 95 percent of the body's volume in water). Brontosaurs and stegosaurs were somewhat thin-thighed, and in cross section their bones are about as thick as we would expect in an elephant of similar size. But Triceratops, Tyrannosaurus, and the other predators were much more massively shafted, far stronger in girth of bone, and these dinosaurs could exert positively prodigious force through their limbs without fear of fracture.

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"AMNH 5027's femur"

Problem is, AMNH 5027 doesn't have a preserved femur

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Oh my god, you're right! I just looked at Hartman's skeletal of it, and no femur!

It's beyond me what Christiansen was doing, then.

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Greg Paul restored it in multiview with drawn femora, he probably gleaned data from it or something.

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So, that leaves room for substantial error when trying to extrapolate strength indicator, doesn't it?

Edit: I looked back at Paul's paper on tyrannosaur leg morphology and locomotion, and it notes that the strength indicator for Tyrannosaurus' femur overestimated the size of the specimen in question, MOR 555. It assumed the animal was 8,000 kilograms, which Paul says it wasn't (closer to 5,400 kg). He says it would have been close in size to specimens AMNH 5027 and AMNH 5207 (I thought the latter was a typo meant to refer to AMNH 5027, but it's mentioned again in The Tyrant King). At 5,700 kg, the strength indicator is actually 13, a little under a 100 kilogram Struthiomimus (which was at 15) that I don't think anyone would doubt could run very fast with a suspended phase.

With Sellers et al.'s paper, I don't think bone strength is as much of an issue for a Tyrannosaurus (given how the long bones articulate) as it would be for an elephant.

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New paper on why big animals aren't fast (Taipan posted it on Carnivora). It gives its own estimated figures for extinct non-avian dinosaur speed with...some sort of model.

Velociraptor-54.56 km/h (46.89-57.82 km/h)
Allosaurus-40.78 km/h (28.93-44.83 km/h)
Tyrannosaurus-27.05 km/h (17.84-31.52 km/h)

b3.ifrm.com/30233/130/0/p3004039/A_general_scaling_law_reveals_why_the_largest_animals_are_not_the_fastest.pdf

The speed figure for the colossal Tyrannosaurus is consistent with it being faster than an elephant, but not an exceptionally fast runner. I, of course, still find estimates on par with or lower than 15 mph (elephant speed) to be bullshit.

The Allosaurus speed figure is also on par with lower bound estimates for brown bears I've read in the scientific literature (40-48 km/h).

[blaze]

There's another new paper analyzing Tyrannosaurus speed, following in the footsteps of Hutchinson's and Seller's work, it now factors bone stresses and once again a walking gait for it is supported, with its accompanying low speeds: peerj.com/articles/3420/

One does have to take into account that elephants are quadrupedal and that the record speeds reached by elephants were achieved by small, young individuals, not 6 tonne bulls,.

Ausar, I don't know if you still hold this view since you wrote it several months ago, but the fact that giant theropod limb bones were not held in a columnar posture actually means that they were subjected to greater stress, it doesn't necessarily follow that the bones had to be relatively stronger, for all we know the thicker shafts of Tyrannosaurus relative to elephants and mammoths were not only the result of the former being bipedal but an adaptation to the "suboptimal" limb posture that it had, as it is seen to a much exaggerated degree in giant birds.


There are some papers whose names escapes me right now, that basically argue that most adaptations deemed "cursorial" don't really correlate with max speed, but rather, are indicatives of increased walking efficiency, something hinted at in this new paper too.

It is somewhat paradoxical that the relatively long and gracile limbs of T. rex—long argued to indicate competent running ability (Bakker, 1986; Christiansen, 1998; Paul, 1998; Paul, 2008)—would actually have mechanically limited it to walking gaits, and indeed maximised its walking speed. This observation illustrates the limitation of approaches that rely solely on analogy and the importance of a full biomechanical analysis when investigating animals with extreme morphologies such as T. rex.

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Blaze you're alive! Are you going to be more active in the future?

Ausar, I don't know if you still hold this view since you wrote it several months ago, but the fact that giant theropod limb bones were not held in a columnar posture actually means that they were subjected to greater stress, it doesn't necessarily follow that the bones had to be relatively stronger, for all we know the thicker shafts of Tyrannosaurus relative to elephants and mammoths were not only the result of the former being bipedal but an adaptation to the "suboptimal" limb posture that it had, as it is seen to a much exaggerated degree in giant birds.

I'm aware of the posture and stress thing. But that doesn't bring down my point.

Yes, the tyrannosaurid's leg bones would need to be thicker shafted because it needs to withstand the greater bending stresses incurred by the more flexed-legged posture. But that also means that when the legs are undergoing stresses incurred by moving relatively fast (or, in a pushing contest or whatever) they will be stronger by virtue of the fact that they have to withstand greater bending stresses just from having a more flexed-legged posture.

This is something I think the new bone strength study suffers from. The Tyrannosaurus in the computer model (which is already oversized and lacks shock absorbing soft tissue, the latter of which has been admitted by the authors) seems to have this rather columnar, graviportal posture. Yeah, the computer might have done this because it thought that this would subject the leg bones to as little stress as possible (the whole point of being graviportal). But having flexed legs allows you to effectively lengthen or shorten the length of your limbs, which is potentially important for reducing stresses subjected to the bones.

And if having thicker leg bones was Tyrannosaurus' way of bearing its weight that made them no stronger than those of elephants, then why were there equivalent sized bipedal flexed legged theropods with leg bones that were less thickly shafted relative to total body mass (the largest carcharodontosaurids, or hell, Spinosaurus, which was still a competent walker on land)? On the converse, why were there quadrupedal animals of elephantine body mass with much stronger and more robust leg bones than what elephants have (like Triceratops, Ankylosaurus, Elasmotherium, even some mastodonts)? Clearly at least T. rex's leg bones didn't need to be as thickly shafted as they were just to bear its weight.

Are you suggesting that the 6.8 m/s I previously mentioned for elephants was not achieved by fully grown animals (so, adult elephants may actually be even slower than that?)?

[blaze]

Are you suggesting that the 6.8 m/s I previously mentioned for elephants was not achieved by fully grown animals (so, adult elephants may actually be even slower than that?)?

Yes, Hutchinson et al. (2003), says that out of the 42 elephants they studied, (all selected out of a pool of 300 for their quickness) only 3 reached speeds over 6m/s (21.6km/h), in the supplementary material we find that they were two males and a female,

6.8 m/s: 17 year old, 2.37m tall bull
6.6m/s: 7 year old, 1.97m tall cow
6.2m/s 3 year old, 1.59m tall cow.

Plotting the data there's a very slight negative relationship between size and speed but there's not enough 3 tonne plus individuals in this sample to be sure, the only ones had rather disparate speeds, at 5.5m/s and 3.6m/s respectively, either way, both are noticeably slower than the young ones above.

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Can you send me the supplementary info? Thanks.

[blaze]

It's here: www.nature.com/nature/journal/v422/n6931/suppinfo/422493a.html

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Gracias! I hope theropod becomes active again soon. I wonder what he'll think of all this new information.

[blaze]

Hopefully.

There's another study that might give some speed compared to this other new studies:
"Using step width to compare locomotor biomechanics between extinct, non-avian theropod dinosaurs and modern obligate bipeds"

Reduction of gait width is not something that was taken into account by Sellers et al. (2017), and of course, there's also the other caveats they mention:

In particular, extending the stress analysis to a full finite element model would be of considerable benefit especially if coupled with a more realistic muscle coverage achieved by subdividing anatomical muscles into multiple functional units and by including other non-bone tissues. These extra elements would potentially allow the model to exploit the possibilities of peak stress reduction using soft tissue tensile elements to produce tensegrity structures (Schilder, 2016) which might turn out to have a substantial effect as has been suggested in other tyrannosaurids (Snively & Russell, 2002a). Finally, our simulations rely on machine learning to find muscle activation patterns that maximise the speed given a range of constraints. There are too many possible combinations of parameters to perform an exhaustive search over all possibilities so we need to use a non-exhaustive approach. This is a very active area of current computational research and we would certainly expect that better solutions will be found using a combination of the improved algorithms and the greater computational power which will be available in future.

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Reduction of gait width? I might have to look into that paper you mentioned, for I don't completely understand it.

Those caveats Sellers et al. (2017) pointed out are interesting, especially the one about non-bone tissues having a positive effect on the tyrannosaur. I recall some news articles saying that the authors didn't take tendon elasticity into account. I guess everything counts.

Also, blaze, I've been meaning to ask you this, but you were inactive at the time. Would you mind making a to-scale comparison between the hindlimb elements of a Tyrannosaurus and the limb elements (fore and hind, I suppose) of an equal sized elephant? I want to see how they compare in terms of thickness and joint size (and maybe other things I'm forgetting right now). Thank you for your time.

[blaze]

It basically means that, for example, in a walking human, each foot falls next to each other but when it is running the feet fall one behind the other, in theropods, including living birds, the same happens as they gain speed. Sellers et al's model always has its feet falling next to each other.

It'll be hard to find proper photos of proboscidean limbs from all views but I'll try.