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Post by Verdugo on Sept 30, 2019 14:02:11 GMT 5
Basically at this stage, which taxa appears to be the champion of heavy biters ? Tyrannosaurus, Deinosuchus or Purussaurus ? Since the method involved is always different. Or were there all in a similar department ? Adding to what Theropod already said, Modelled (Sustained/Static) BF of T-rex is usually higher than that of scaled up Gator too. For example, in Bates 2012, the adult Gator in that has a BF of 5761 N and mass probably ~250 kg. Scaling those up to Stan's mass of 7000 kg, we will get ~53000 N, which is slightly less than the 57000 N of Stan In Sellers 2017, they estimated the BF of 4500 N for a ~250 kg Gator. Scaling that up to Stan's mass of 7000 kg, we will get ~41000 N, which is actually a good deal less than the 63000 N of Stan in Cost 2019 (Cost 2019 also used the same 3D level method as Sellers 2017, same specific tension data too) While i don't think it's conclusive, it does seem to suggest that T-rex could actually bite harder, even on lb 4 lb basis. The larger T-rex with wider skull such as Sue is likely to bite even harder than Stan could do. Or if you don't want to concern about all the convoluted process of BF stuffs and you just want to take the 'official' figures at their face value, then Deinosuchus is still hardest biter at ~100 kN in Erickson 2012 |
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Post by Grey on Sept 30, 2019 14:20:06 GMT 5
Why was Deinosuchus estimated as high as this ? Was it peak bite force ?
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Post by theropod on Oct 1, 2019 3:41:26 GMT 5
Yes, it was peak bite force, all of Erickson et al.’s BF figures were. But we were already talking about peak bite forces for T. rex too, in the most recent comments, so that’s not the issue.
That they came up with such a high estimate is really quite strange.
First of all, they used a very weird Deinosuchus, 11 m TL, 3,450 kg. While 11 m appears quite realistic for a record-sized Deinosuchus, I don’t think just 3.5 t at that length is realistic in the slightest This seems to be because they regressed mean mass against TL, rather than the actual masses of specimens. However, when I use their equation for estimating body mass, I’m actually getting 4,600 kg at 11 m (5.00*11^2.846), not 3450 kg as they claim. No idea why that is, can someone check my numbers please? At any rate, a more realistic weight estimate at 11 m would be closer to 6 t. So their mass estimate should theoretically lead to underestimates.
Then again, as I pointed out already, their regression methodology is flawed, or at the very least highly misleading. They didn’t regress the bite force of individual specimens against the weight of those same specimens, they regressed mean bite force of the respective taxa against mean weight. So the result would not actually be an estimate of the bite force of a specimen with the given body weight, but the mean bite force of a taxon with the given mean body weight. Generally this should tend to lead to underestimates because mathematically, mean mass will correspond to a larger animal than mean BF. But additionally, in some cases, where they measured just one specimen, both are the same, in others they aren’t, which can have unpredictable results.
But most importantly, as Verdugo pointed out, they used a linear model for their estimates (29.632(body mass, kg)+569.35), which is also unrealistic for the scaling of bite force. They report also using a more model with more realistic scaling based on a saltie growth series, (115.39*BM[kg]^0.7629), but they just seem to have either not used it for Deinosuchus, or ignored that it yields a completely different figure than the one they report, 57,699.28 N (which is far more realistic already). A linear model in this case leads to major overestimates, because it assumes an exponent of 1, when the exponent of isometry is 2/3.
This 10t figure however is indeed what their linear equation yields: 29.632*3450kg+569.35 = 102,799.8 N
The slight difference to the printed figure of 102,803 N must be because they used an exact mass figure while only reporting a rounded one for me to use.
We’ve discussed this at length, and I’ve attempted to correct this by log-transforming the data and fitting a model to only the maximum weights and bite forces (under the, as I think, reasonable assumption that these correspond to the same specimens). The resulting model was 147.766*BM[kg]^0.7116, R²=0.922. So this is a fairly close (if understandably slightly lower) fit for the exponent of the saltie regression Erickson et al. used, and only slightly above isometry.
Of course the sample size is not very large, and it is taxonomically diverse, so accordingly error margins are large, but based on this model, a 3450 kg crocodilian (the size they estimated) would actually be expected to have a (posterior) bite force of 48637.62 N (50% PI 40361.71-58610.46), and a 6 ton one (probably a more realistic mass for the largest Deinosuchus) 72108.24 N (50% PI 59171.04-87874.05).
At any rate, I would not trust Erickson et al.’s figure for Deinosuchus due to the numerous issues with it, especially the use of an entirely unrealistic form of model, at least for extrapolating this far. I would propose that, with the obvious caveat of large error margins inherent in such extrapolations, the estimates based on the model I fitted are likely fairly good for what we can do with the available data, but the regression based on the captive saltie growth series should also be considered (this would point towards the upper end of that 50% PI for Deinosuchus, at 88007.52 N for 6 t).
That’s the problem if we un-reflectively only accept the highest published figures. Some of them may be flawed, and important taxa (such as very large pliosaurs, or Livyatan) may not be represented. But if we unquestioningly do so, we’d also have to accept Meers’ estimate for T. rex (which is of course utter BS), which remains the highest published bite force estimate I am aware of for any taxon.
Based on available data, I tend to think large T. rex and the largest currently known crocodilians bit with fairly similar amounts of (posterior) bite force. The only things that I would definitely expect to bite noticeably harder would be Livyatan, meg and probably the largest pliosaurs (McHenry’s upper estimate for the Harvard Kronosaurus’ body mass would suggest 118873.36 N (96057.39-147108.67) based on the adjusted regression for Erickson et al.).
As mentioned before, we should remain very curious about Moon’s unpublished estimate for Temnodontosaurus, as based on that we could realistically expect at least similar bite forces to T. rex and giant crocodilians for the largest lower Jurassic Ichthyosaurs (and that’s likely not considering peak bite forces, and might be comparatively conservative as it looks like it is dry-skull based). I’d also be very curious about the bite force of some mosasaurs, especially Prognathodon, since it’s skull reaches a similar size to that of T. rex, and a similar bite force seems plausible based on it’s overall robusticity.
I think that’s pretty much it, I cannot think of much else to rival these. Other giant theropods and Basilosaurus would have probably bitten harder than pretty much anything alive today (save, perhaps, a very large orca), but comparative data suggest somewhat lower BF for these than the aforementioned taxa.
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Post by Verdugo on Oct 1, 2019 13:51:40 GMT 5
As mentioned before, we should remain very curious about Moon’s unpublished estimate for Temnodontosaurus, as based on that we could realistically expect at least similar bite forces to T. rex and giant crocodilians for the largest lower Jurassic Ichthyosaurs (and that’s likely not considering peak bite forces, and might be comparatively conservative as it looks like it is dry-skull based). To be fair, i don't think it's necessary at this point to distinguish 2D dry skull vs 3D method anymore. Most of the times, researchers don't usually even bother distinguishing the two. The whole 2D vs 3D concept is not exactly that well-defined in literature either. And 2D methods are not always 'conservative' or produce lower estimates than 3D ones.I think the main distinction we should make is between pennation and non-pennation models. Pennation can indeed drastically affect BF estimates. Both 2D and 3D models can either account or not account for pennation so we need to keep this in mind. I’d also be very curious about the bite force of some mosasaurs, especially Prognathodon, since it’s skull reaches a similar size to that of T. rex, and a similar bite force seems plausible based on it’s overall robusticity. Prognathodon's skull appears to be quite similar to Tegu's. Perhaps one could try extrapolating it based on Tegu's in vivo data (i have seen some studies of Tegu in vivo). It may not be appropriate but it may still able to give us some general idea of Prognathodon's BF I think that’s pretty much it, I cannot think of much else to rival these. Other giant theropods and Basilosaurus would have probably bitten harder than pretty much anything alive today (save, perhaps, a very large orca), but comparative data suggest somewhat lower BF for these than the aforementioned taxa. Are there any reasons why we don't have any data for Orca BF at all? Sea World has been training the Orcas for ages. Couldn't researchers just contact Sea World and request them to have the Orca BF measured? Would actually be easier than spending hours trying to restrain a half tonne Saltie. Animals rights issues i suppose |
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Post by creature386 on Oct 1, 2019 15:03:03 GMT 5
Are there any reasons why we don't have any data for Orca BF at all? Sea World has been training the Orcas for ages. Couldn't researchers just contact Sea World and request them to have the Orca BF measured? Would actually be easier than spending hours trying to restrain a half tonne Saltie. Animals rights issues i suppose While I don't understand either why we have no such data, I don't think we'd really want it that badly. It'd be hard to compare to all the other data we typically look at. For example, whenever the great white shark's bite force comes up, it's the 1.8 t figure from Wroe's paper, not an actual in vivo measurement. |
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Post by theropod on Oct 1, 2019 21:22:28 GMT 5
Verdugo: 1) Yes, my point was mainly that the estimate is unlikely to be peak bite force. It is not necessarily subject to the other reasons causing underestimate in dry skull estimates, but is also isn’t necessarily not subject to them. We don’t have much detail on the figure, sadly. 2) That is an excellent idea, I’ll look into that. 3) The total absence of studies on this is is very puzzling. While it might not be so easy to get a captive orca to bite as hard as it can into something (crocodiles generally need little encouragement to bite, but orcas are far less aggressive towards humans, and might not be inclined to bite, let alone with full force), I’m sure it could be done somehow. Also, there should theoretically be ample information on all aspects of orca anatomy and physiology. While it would obviously be difficult to ct-scan a live orca, it would appear more than feasible to do so with the head of a dead (e.g. stranded or diet in captivity) one, so if in vivo measurements weren’t an option, modelling could be. No idea. It just seems like functional morphology of the feeding apparatus is really underrepresented in orca research. Animal rights issues don’t seem like a likely explanation to me. It’s far less of an animal rights issue to stick a measurement device into its mouth to measure bite force than it is to keep orcas in captivity in the first place. It rather looks like the bite gets continually overlooked. Everything else about orcas is widely studied. Just jaw mechanics never are.
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Post by theropod on Oct 1, 2019 21:59:23 GMT 5
2) Hmm, problem seems to be that while there is a large number of in vivo bite force measurements for Tegus, neither are the figures themselves available as a dataset, nor are accompanying measurements of the animals. This study measured quite a lot of tegu bites: repositorio.unesp.br/bitstream/handle/11449/21155/WOS000270695800006.pdfHowever they focused on behavioural correlates of bite force, not the actual figure or its relation to body or skull size. Very interesting, but a little frustrating if we want to use the data to estimate bite force from skull size or body mass. They also list a correlation of BF with SVL, so they must have measured the latter, but they don’t seem to show it anywhere. From their plots we can see that the maximum bite force of the male Tegus they measured is around 1000 N, but this doesn’t help a lot without knowing the size of the tegu. |
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Post by Infinity Blade on Oct 5, 2019 7:37:16 GMT 5
It apparently took only 6,410 N for a T. rex to make indentations into the pelvis of a Triceratops. This same pelvis also had a sixth of the ilium removed by what was apparently repetitive biting. Would biting off this piece have involved the same aforementioned levels of force? Actually, is this question not applicable because it's suspected to have involved repetitive bites? sci-hub.tw/10.1038/382706a0I ask because I think this a rather large, solid piece of bone, and yet only a fraction of the tyrannosaur's actual bite force was necessary to bite it off. At least, that's the impression I'm getting. |
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Post by theropod on Oct 5, 2019 13:31:41 GMT 5
It apparently took only 6,410 N for a T. rex to make indentations into the pelvis of a Triceratops. This same pelvis also had a sixth of the ilium removed by what was apparently repetitive biting. Would biting off this piece have involved the same aforementioned levels of force? Actually, is this question not applicable because it's suspected to have involved repetitive bites? sci-hub.tw/10.1038/382706a0I ask because I think this a rather large, solid piece of bone, and yet only a fraction of the tyrannosaur's actual bite force was necessary to bite it off. At least, that's the impression I'm getting. This estimate was for a specific bite mark, made by a single tooth. Achieving the same penetration depth with several teeth at once would require higher bite forces. |
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Post by Verdugo on Oct 6, 2019 11:18:08 GMT 5
It apparently took only 6,410 N for a T. rex to make indentations into the pelvis of a Triceratops. This same pelvis also had a sixth of the ilium removed by what was apparently repetitive biting. Would biting off this piece have involved the same aforementioned levels of force? Actually, is this question not applicable because it's suspected to have involved repetitive bites? sci-hub.tw/10.1038/382706a0I ask because I think this a rather large, solid piece of bone, and yet only a fraction of the tyrannosaur's actual bite force was necessary to bite it off. At least, that's the impression I'm getting. Pretty much everything Theropod said. It takes the Pressure of 6400 N per Surface Area of One Tooth to create that indentation. If T-rex bites down with more than one tooth, it will need correspondingly higher Force just to generate that Pressure (6400 N/One Tooth). Realistically, i think it's impossible for T-rex to bite with just one tooth, i mean the bare minimum it needs would be two, one upper and one lower. Rayfield (2004) followed this idea and she extrapolated the force to the entire upper tooth row and she got like 150 kN (bilaterally) (her extrapolation may be a bit too far though) And for how much damages can T-rex cause with its bite? www.youtube.com/watch?v=6_Vv5G0VTQI&t=90sThe simulation from this show is still one of my fav for several reasons: 1. Like the host said, the T-rex model can actually snap its jaw so it's more akin to in vivo than just static bite (though the Snapping velocity here might still be too low) 2. The cow bones here are wet bones and not dry bones (which are less realistic) like some of the other tests i have seen In the program, they said the BF was about 4 tonnes. Now i don't think that is the actual BF but it's probably just the force they loaded to the pistons. So you can think of it like Muscle Force (the actual molariform BF would have been lower when taking into account of level arms). Cost (2019) estimated the Muscle force of T-rex up to 120 kN (table 2). So the test here should be considered conservative. Obviously, T-rex should be able to chomp down much larger bones than just those cow bones here |
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Post by theropod on Oct 6, 2019 15:50:47 GMT 5
Yes we cannot really convert it like that, there is no way of knowing precisely with how many teeth it would have bitten, and how each of them was loaded. As impossible as it would likely be to bite with only a single tooth (as you point out there would likely be an opposing tooth that would achieve some sort of penetration as well), as impossible would it be to bite with all teeth at the same time and with the same force. Whatever it bit would either have sufficient curvature so only part of the tooth row would make contact, or be so large in girth that gape angle would have to be so large the bite would be less forceful.
Such single-tooth values are simply lower bound estimates for the total force the animal must have produced. Neither do they tell us anything about the maximum, nor do they really differentiate between what was bite force and what was postcranial force.
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Post by Infinity Blade on Oct 6, 2019 19:21:54 GMT 5
It apparently took only 6,410 N for a T. rex to make indentations into the pelvis of a Triceratops. This same pelvis also had a sixth of the ilium removed by what was apparently repetitive biting. Would biting off this piece have involved the same aforementioned levels of force? Actually, is this question not applicable because it's suspected to have involved repetitive bites? sci-hub.tw/10.1038/382706a0I ask because I think this a rather large, solid piece of bone, and yet only a fraction of the tyrannosaur's actual bite force was necessary to bite it off. At least, that's the impression I'm getting. Pretty much everything Theropod said. It takes the Pressure of 6400 N per Surface Area of One Tooth to create that indentation. If T-rex bites down with more than one tooth, it will need correspondingly higher Force just to generate that Pressure (6400 N/One Tooth). Realistically, i think it's impossible for T-rex to bite with just one tooth, i mean the bare minimum it needs would be two, one upper and one lower. Rayfield (2004) followed this idea and she extrapolated the force to the entire upper tooth row and she got like 150 kN (bilaterally) (her extrapolation may be a bit too far though) And for how much damages can T-rex cause with its bite? www.youtube.com/watch?v=6_Vv5G0VTQI&t=90sThe simulation from this show is still one of my fav for several reasons: 1. Like the host said, the T-rex model can actually snap its jaw so it's more akin to in vivo than just static bite (though the Snapping velocity here might still be too low) 2. The cow bones here are wet bones and not dry bones (which are less realistic) like some of the other tests i have seen In the program, they said the BF was about 4 tonnes. Now i don't think that is the actual BF but it's probably just the force they loaded to the pistons. So you can think of it like Muscle Force (the actual molariform BF would have been lower when taking into account of level arms). Cost (2019) estimated the Muscle force of T-rex up to 120 kN (table 2). So the test here should be considered conservative. Obviously, T-rex should be able to chomp down much larger bones than just those cow bones here Yeah, I remember that simulation. Slight tangent, but the only real gripe I have is the fact that they used a steel skull cast. Like, obviously I have no problem believing a real T. rex could effortlessly crush cow bones, but then they decided to test it against a car (which it also destroyed). They were able to make the Triceratops skull out of resin (I'm not sure how much that mimics the strength of bone), so was it or was it not possible for them to use something that more closely mimics bone for the T. rex skull? |
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Post by theropod on Oct 9, 2019 16:47:58 GMT 5
Theropod, no I meant big fish. In a manner similar to Spinosaurus. A long narrow jaw helps in catching big fish too. Grey, the megalodon reconstruction you posted is an extreme case. "Proportionally bigger" head in comparison to GWS doesn't need to look like that. The second point is true. About big fish, other large marine predators would prey on those, or similar-sized prey as well. So why would that create a unique selective pressure on pliosaur jaws? |
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Post by dinosauria101 on Oct 9, 2019 20:02:12 GMT 5
Why is that? I thought pliosaurs and mosasaurs could just bite chunks Well, their jaws look similar enough to crocodile jaws. And a crocodile typically has a hard time bitting chunks off a large surface. They need to perform a death roll in order to do it. Apologies, missed this and gave a scrappy reply later on. Now that the kerfuffle of threads is over, I can give a good and direct response. Most mosasaurs and pliosaurs have serrations on their teeth; this would probably allow for them to preform 'shark-style' feeding with crocodile like jaws Kronosaurus is perhaps the exception; I think it would have done something intermediate of sharks and crocodiles; its teeth lacked serrations but were much sharper than crocodile teeth. Probably could tear off flesh with no rolling, but needed a good grip first. |
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Post by sam1 on Oct 10, 2019 2:27:03 GMT 5
Well, their jaws look similar enough to crocodile jaws. And a crocodile typically has a hard time bitting chunks off a large surface. They need to perform a death roll in order to do it. Apologies, missed this and gave a scrappy reply later on. Now that the kerfuffle of threads is over, I can give a good and direct response. Most mosasaurs and pliosaurs have serrations on their teeth; this would probably allow for them to preform 'shark-style' feeding with crocodile like jaws Kronosaurus is perhaps the exception; I think it would have done something intermediate of sharks and crocodiles; its teeth lacked serrations but were much sharper than crocodile teeth. Probably could tear off flesh with no rolling, but needed a good grip first. I don't see the need for apology. The serrations are a good point. But still, as a whole, the long and narrow jaw simply isn't a good mechanical solution for slicing into a large flat surface..serrated teeth ain't gonna change that fact. They would certainly help in cutting a fish in half though. |
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