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Post by Infinity Blade on Jun 29, 2018 19:05:54 GMT 5
It’s really weird to have a clearer picture of the biting mechanics of Basilosaurus or Pliosaurus than we do of an extant cetacean with a cosmopolitan distribution that’s literally being held in zoos. Yeah, frankly Basilosaurus and Pliosaurus are really just two random aquatic predator genera that have been extinct for millions of years with each species thereof only known from God knows how relatively few and incomplete remains. Even if they themselves are also fascinating animals, it's weird that we know more about their jaw apparata than we do with the orca's for the reasons you mentioned. Anyway, what do you think of the question I posed in the last post? |
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Post by Infinity Blade on Jun 30, 2018 1:49:40 GMT 5
More T. rex vs. jaguar at probable parity comparisons, this time with jaw muscles. As with last time I just did copying and pasting on a Word doc and modeled the lengths of the skulls after the previous ones as best as I could.  The T. rex is from Gignac & Erickson (2017) while the jaguar is from Hartstone-Rose et al. (2012).  The T. rex was created by Yeager (2016) (clickable; he also had a YouTube video with the jaw muscle reconstruction) and the jaguar is again from Hartstone-Rose et al. I used two different myological reconstructions for Rexy because it seems not every reconstruction is the same (understandable, since Tyrannosaurus is extinct). The jaguar on the other hand is an extant animal and so myological reconstructions shouldn't suffer this problem. Also, I might have made a mistake with the jaguar. I noticed theropod said condylobasal length for the jaguar skulls he found, but these are scaled to ~125 cm in total length. So I do think the jag skulls are somewhat oversized, though not by too much. I imagined the jaguar's skull would have an edge in mechanical advantage given how short and broad its snout is (ergo, it's a comparatively short way off from the canines to the jaw closing muscles). But it's interesting how the tyrannosaur is reconstructed with jaw adductors either originating or inserting onto places that are really close behind the toothrow as well. Edit: a friend on Discord created a hypothetical skull size comparison for me. I trust his size comp. skills more than my own, so here it is ( link). |
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Post by theropod on Jun 30, 2018 4:29:51 GMT 5
^Yes those were condylobasal length. So if you scaled to maximum length, the resulting skull is actually a bit undersized, not oversized, as the sagittal crest extends posteriorly beyond the occipital condyle.
Obviously T. rex couldn’t have had a terribly inefficient mechanical advantage for jaw-closing, but I would still wager the jaguar’s is higher on the whole. I mean, it literally looks like the jaguar’s canines are about as far from the muscle insertions as the tyrannosaur’s posteriormost teeth. Of course the jaguar’s jaw is a lot shorter on the whole though, including the in-lever. I’m just eyeballing here. You could try measuring that and calculating the mechanical advantages of course. For that, you’d also have to figure in the relative contraction force of each muscle involved though.
Regarding theropods having more damaging bites, I think back then I was referring to some concrete example of a small or mid-sized theropod being compared to a large felid back on carnivora, at something resembling size parity.
Back then it seemed like the theropod had by far the (dimensionally, not necessarily mass-wise) larger skull and tooth-row, as well as more flesh-tearing capacity, which translates to more damage. And I think the same does, to some extent, apply here as well, although I must admit I do find the jaguar specifically pretty impressive (more because of how it tends to use its bite than how its functional anatomy might differ from other cats).
In general, I know of no non-avian theropod adapted to the style of precision-biting employed by cats. I know I have at times suggested this as an option should a spinosaurine absolutely need to take on something its own size, but that would certainly have been an unusual ocurrence and not the primary purpose of its jaws, let alone within its normal behavioral capacity. Simply put, if your instruments of engaging your prey are just plain old conical teeth, your options of causing mechanical damage are limited, even if your bite is very powerful. You can puncture flesh and bone really well with them, but even the longest teeth don’t penetrate so deeply that they are effective for puncturing internal organs in a large or gigantic prey item.
Cat’s don’t disembowel their prey with their bites, and they don’t usually bite to break major bones either (if I’m not mistaken, the jaguar is actually a bit of an exception on the latter point), at best they will precision-puncture the skull or spine, or even just use their jaws to collapse the trachea and suffocate their prey. T. rex evidently bit through large bones (such as Triceratops horns) during prey acquisition, as well as feeding. I don’t think cats are known to do anything similar (a lion biting off the horn of a buffalo, or biting its leg to immobilise it? never heard of that).
I think your comparisons illustrate what I mean, T. rex still has a bigger bite, and would have caused both bigger wounds and more damage literally anywhere it bit. Note that I think that especially in a primarily meat-tearing organism, wound length is a determining factor, which lends itself perfectly to pull-and-tear style biting. For T. rex, as one of the more durophagous theropods, it may not have been quite as relevant, but T. rex also isn’t a good cat analogue.
T. rex teeth are blunt-edged, but they are still edged (yes, carnassial teeth are edged, I know. But those are in a really ineffective position to be used as, the long canines and relatively short gape simply seem to preclude their use in this manner. Otherwise I’d expect cats to use their undeniably powerful bites to break bones or shear off big chunks of flesh whenever it’s convenient).
Jaguars are afaik among the more damaging biters among cats, largely because of their skull- and turtle-crushing habits as opposed to the throat bites preferred by lions or leopards (I’m slightly venturing out of my comfort zone regarding cat behaviour here, so someone please correct me if I’m wrong). I’m not saying this is a particularly good example of a theropod-over-cat biting-superiority-situation, but in general comparing a biting apparatus evolved to finish-off already subdued animals by precision biting to one evolved to subdue animals by causing massive damage is like comparing a dagger to a longsword. You can’t necessarily thrust more powerfully with the sword (perhaps even the opposite), but it gives you much greater options of attack on various parts of the body because is causes more damage more easily. Of course if it’s not just a comparison between bites, but between the predators as a whole, then it becomes a whole different story, but that is a subject for the limb-function thread. And it’s really irrelevant because an isometrically scaled 8.4t jaguar probably couldn’t even stand, and would slowly suffocate under its own weight.
So if you were asking me whether I’d rather be bitten in the leg by a 30 kilo leopard, or a 30 kilo komodo dragon, or a hypothetical 30 kilo Allosaurus, I think I’d still pick the leopard.
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Post by Infinity Blade on Jun 30, 2018 7:27:33 GMT 5
Ugh, right. I obviously wasn't thinking clearly when I said that.
Well, while I agree I'd probably pick the jaguar if I had to choose which I thought had the superior mechanical advantage (that short snout really sells it) the insertion of the M. intramandibularis (only clearly shown in Gignac & Erickson’s reconstruction) seems to be right underneath the posteriormost teeth of T. rex. The distance between that and the tyrannosaur’s maxillary teeth (arguably the deadliest teeth in a tyrannosaur’s mouth) and the corresponding dentary teeth below is really short too; it actually seems even shorter than the distance between the jag’s closest masseter insertion and the tip of its lower canine. The distance between the intramandibularis and the anteriormost teeth itself seems pretty short too. Of course, I’m just eyeballing too and so my judgements are probably no better than yours.
Wait, is there an actual fossil suggestive of Tyrannosaurus biting a leg to immobilize a prey item? I'm certainly aware of the bitten horn, but this is new to me (though certainly not surprising).
Skull biting by lions (and cougars, so possibly extending to leopards as well) is not unheard of, but I would still think the jaguar is more of the skull and carapace crushing cat out of them all. Even anatomically the jaguar seems to be somewhat more predisposed for it. Like I said earlier, Hartstone-Rose et al.'s results suggest that, while a jaguar has an absolutely weaker bite than a tiger twice its weight, the former actually ends up biting harder when corrected for size.
Of course. On the converse, a 100 kilogram Tyrannosaurus is either a juvenile (the only way you'd realistically get a T. rex that small) or a fantasy scaled down adult that would probably freeze to death. I only meant this as a fantasy hypothetical of sorts.
Regarding the other parts of your post, they make sense to me.
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Post by theropod on Jun 30, 2018 21:42:31 GMT 5
No I wasn’t suggesting any direct evidence that T. rex did that, if there is I’m not aware of it. I think it could have, though. Greg Paul suggested something similar in his chapter in 'The Tyrant King' (Paul 2008, fig. 18.7) too, and it makes a lot of sense to me, as you wouldn’t want to attack a Triceratops from the front if you could help it, rather bite its hindlimb or hip to immobilise it. While I would think that causing soft-tissue wounds the way Paul envisions it would would not be hugely effective for T. rex (though certainly more so than a felid trying to do the same thing), I think there are a variety of bones in the limbs or limb girdles that it may have the capacity to bite and critically damage.
Regarding the M. intramandibularis, Molnar (2008) wrote he could not find any evidence of its existence in T. rex, apparently it’s present in crocodiles, but absent in most or all birds. Gignac & Erickson (2017) seem to think it was present, but concede that the osteological evidence is faint, so I’m not sure how well-constrained the reconstructed insertion point can possibly be. Also according to Molnar, its function is unclear, but it doesn’t seem to constribute to jaw adduction.
Gignac, P. M., and G. M. Erickson. 2017: The Biomechanics Behind Extreme Osteophagy in Tyrannosaurus rex. Scientific Reports 7:2012.
Molnar, R. E. 2008: Reconstruction of the jaw musculature of Tyrannosaurus rex.Tyrannosaurus rex: the tyrant king. Indiana University Press, Bloomington, Indiana:254–81.
Paul, G. S., P. Larson, and K. Carpenter. 2008: The extreme lifestyles and habits of the gigantic tyrannosaurid superpredators of the Late Cretaceous of North America and Asia. Tyrannosaurus rex: the tyrant king. Indiana University Press, Bloomington, Indiana:307–353.
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Post by Infinity Blade on Jul 1, 2018 0:48:42 GMT 5
I checked Molnar's work, and something about it confuses me.  So as you can see, it lists the M. intramandibularis in table 15.2 and the corresponding description labels it as a jaw abductor (along with everything else in the list). But further down the text labels them as jaw adductors. Typo? Something I don't know? I'm still confused on just how hard Tyrannosaurus bit at what tooth position and at what body size (ergo, at what skull size). There are extremes I think we can rule out; I am almost 100% sure that an 8,400 kilogram Tyrannosaurus (Sue; see Table 1 of Gignac & Erickson*) would not merely bite with a force as "low" as 17,769 Newtons anywhere on its toothrow (even if it's not brevirostrine to the extent of say, cats) nor anywhere as hideously massive as 235 kN or 300 kN (even if it were an animal optimized for biting down hard). There's apparently in vivo and biomechanical model estimate results to take into account (that excerpt from Snively et al. I quoted seems to hint a bit at that), as well as peak vs. sustained force. The whole thing feels like a mess to me, honestly. *Although, their skull measurements for Sue seem kind of off, so I wonder if that has anything to do with it. |
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Post by theropod on Jul 1, 2018 3:34:47 GMT 5
On page 273, in the section devoted to that muscle, Molnar discusses its function, stating "The M. Intramandibularis, if present, might have acted to operate an intramandibular joint (if such existed in T. rex" (actually Hurum & Currie studied that joint in 2000 and concluded its range of motion was ), then conceding this is purely hypothetical as the insertions are unknown, and "Alternatively, it might have also acted to resist anteriorly directed forces on the jaw exerted [sic] by prey." (Not sure how exactly that would work though).
He also writes its function in crocodiles, and in ostriches (where it might be present) is unknown. So either way we know too little about that muscle to make much of a solid inference, but it’s probably not an important jaw closer.
It certainly is a mess. I think the lesson from all of this is that no absolute bite force estimate for an extinct taxon can really be taken at face value (much like with running speed estimates), but that they are to be treated as either vaguely indicative lower or upper bound estimates, or as useful means of comparison between taxa that have been studied using the same methodology.
However, I think the 18-30 t figures are ridiculous. And I think that much at least could probably be demonstrated by running the skull through FEA and testing whether it could withstand the kind of stress imposed by such a bite force.
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Post by Infinity Blade on Jul 1, 2018 5:21:28 GMT 5
At least one person I remember back on Carnivora (Vodmeister) seems to be aware of the need to remain consistent (i.e. comparing taxa measured with the same methodology) when comparing bite force among different taxa. I think he was discussing big cat vs. bear bite force then. By that same token, I'm no longer sure that a comparison between the numbers of Bates & Falkingham (or Gignac & Erickson, or whomever) and Hartstone-Rose et al. is very meaningful. I hope someone one day compares a bunch of different and unrelated vertebrate predator taxa into one bite force study (i.e. integrating Mesozoic theropods, carnivorans, etc.), just so we get some idea of how hard these animals should be biting compared to one another (relative bite forces, if accurate body mass estimates are provided, can then be inferred by us, or flat out given to us via bite force quotient) all under one methodology. If no one does that, then maybe that's something I'd be interested in doing later in life; I know, I've only recently passed my first year of college (and this is a rather ambitious goal), but a guy can dream lol! Until then, it seems that bite force comparisons between different animals should be taken with a grain of salt, particularly if the figures were not obtained with the same methodology. Without such data, logic and a bit of intuition (read: some knowledge on what would or wouldn't be conducive to a harder bite) are probably left as our best friends (i.e. simple logic would indicate that an adult Tyrannosaurus rex would bite absolutely far harder than a jaguar, while Livyatan would in turn bite absolutely far harder than a T. rex, let alone a jaguar, or that any of these predators have an absolutely powerful bite to begin with). To add another contribution to the thread, here is one study that does integrate multiple different (North American) carnivoran taxa for bite force. www.nlc-bnc.ca/obj/s4/f2/dsk1/tape2/PQDD_0014/MQ61307.pdf |
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Post by Infinity Blade on Jul 3, 2018 6:49:54 GMT 5
This is from Sakamoto (2010). It says tyrannosaurids ( Tyrannosaurus in particular) retained mechanical advantage across their toothrow better than other theropods. Does this mean all around superior mechanical advantage? I'm not sure I fully understand the part about oviraptorosaurs either. Earlier it says: " The vertical position of the profile (β0) relates to the proximity of the tooth row to the jaw muscles, while the slope (β1) relates to the length of the tooth row.Is their mechanical advantage actually inferior to other high-efficiency biters (which this study found to be the ceratosaurs, allosaurs, and tyrannosaurs)? rspb.royalsocietypublishing.org/content/277/1698/3327#F2--------------------------------------------------------------------------------------------------- Also, about FEA on T. rex's skull. I remembered that Emily Rayfield did an analysis on the shock absorbing sutures in Tyrannosaurus' skull. What I didn't realize was that she had a little tidbit on absolute bite force. Vertebrate Paleontology (clickable) " In her FEA model of the T. rex skull, Erickson et al.'s (1996) bite forces of around 31,000 N (equivalent to 78,060 N along all the teeth in a single jaw, and 156,120 N for both jaws together) were applied to individual teeth, and the distortion of the element mesh was observed...In reality all teeth would almost certainly not be operating at their maximum possible force together, so Rayfield (2004) estimates a maximum-single tooth bite force of 31,000 N..." Cranial mechanics and feeding in Tyrannosaurus rex (clickable) " Tyrannosaurus rex may have been capable of generating 13 400 N bite force at a single posterior tooth (Erickson et al. 1996). Using moment arm calculations to extrapolate this value rostrally along the tooth row, a total of 78 060 N was divided between biting teeth (therefore assuming 156 120 N bilaterally, less than, but approaching, values estimated by Meers (2002)). However, it may be argued that being first to contact a prey item, the large caniniform teeth received the majority of bite force (sensu Rayfield et al. 2001). In accordance with this suggestion, the two large caniniform teeth (figure 1b) were allocated 13 000 N each, while the smaller incisiform and posterior maxillary teeth were allocated lesser values scaled to the size of the teeth. In this model a total of 31 000 N was applied." This is under (e) Bite force magnitude and distributionSomeone had likened this to placing each of your two feet on a different scale. If you weigh a total of 60 kilograms (by analogy, total bite force), one scale (by analogy, one tooth) will read 30 kilograms (by analogy, 13,000 Newtons on one caniniform tooth). So while this is suggesting total bite force may be over 150 kN, it's not as if every single tooth will be punching through flesh or bone with that maximum force. I assume her FEA T. rex skull was able to take the stress, given how she concluded that the skull of Tyrannosaurus was equally adapted to biting and tearing. But, given my post above, what do I know? Also:  compbiomechblog.blogspot.com/p/finite-element-models_7567.htmlIt turns out Stephen Wroe has done 3D computer FEA on T. rex's skull (like he has done with a bunch of mammalian carnivores, sharks, and hominids). I'm having trouble finding out what study this came from, let alone how much stress the analysis found the skull could take during biting. |
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Post by marsupial on Jul 3, 2018 9:42:25 GMT 5
Here are some bite force studies of carnivorous and omnivorous mammals.
htt://www.ncbi.nlm.nih.gov/pmc/articles/PMC1564077/
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Post by theropod on Jul 3, 2018 16:21:09 GMT 5
Actually it’s the reverse, the estimated values were for a single tooth and Rayfield extrapolated that to the entire tooth row.
The FE-model in Rayfield 2006 is just 2d, because she used it to evaluate stress distribution, not maximum strength. So we don’t really know the maximum strength of the skull, even though from that image it appears that some other work may have the answer for us. Better still, that looks like sue’s skull. I’m wondering if that might be from McHenry 2009, I have to check that
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Post by Infinity Blade on Jul 6, 2018 17:30:05 GMT 5
Albertosaurines seem to have had laterally compressed teeth, more like those of juvenile Tyrannosaurus and most other predatory dinosaurs than those of their more famous relative. "The teeth are all laterally compressed, like Nanotyrannus, Albertosaurus, and Gorgosaurus, but not as compressed as in these genera." Correct me if I'm wrong, but if I remember correctly albertosaurine skulls were not quite as adapted to bite hard as the skulls of bone crushing tyrannosaurines. Recent skeletals made by randomdinos on DeviantArt suggest they weren't quite as large headed as well, which would suggest relatively lower bite strength (though obviously still enormous; I mean, their skulls still look like they're more adapted for biting hard than most other theropod crania). Slicing teeth suggest a differing, but just as deadly, hunting/killing method. Reference:Stein, Walter W.; Triebold, Michael (2010). Preliminary Analysis of a Sub-adult Tyrannosaurid Skeleton from the Judith River Formation of Petroleum County, Montana. Tyrannosaurid Paleobiology. Indiana University Press, Bloomington, Indiana: 68. |
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Post by Infinity Blade on Jul 12, 2018 7:24:37 GMT 5
A few things in this post here. First, have you had any luck finding where that 3D FE model of Tyrannosaurus' skull, theropod? I tried looking a couple times, once before I shared it here and the other just a few days ago. I could only trace it back to that same website I originally found it in. Is it possible they just created that for brief observational purposes and not to publish? Second, FE analysis of different felid skulls from Chamoli and Wroe (2011; PDF). Interesting finding regarding the cheetah. Third, I’ve thought about it for a bit, and yeah, I’m definitely still convinced a macrophagous tyrannosaurid would, relatively speaking, have a far more damaging bite than a conical toothed cat (whether it has slicing teeth, as albertosaurines seemed to, or those serrated spikes for teeth). Those with laterally compressed teeth (albertosaurines) could easily slice out a huge chunk of flesh with their big mouths and relatively powerful bites. The ones with those incrassate serrated spikes for teeth (e.g. Tyrannosaurus) may not be able to dish out damage to flesh as economically as most other macrophagous theropods, but a) they will certainly crush and shatter bones more economically than all others and b) horrific soft tissue damage will eventually happen, as “crushing jawed” predators like hyenas and orcas demonstrate today. I’m in agreement that the theropod’s much bigger bite - conferred by a relatively bigger head and jaw shape - will allow it to create much larger wounds, regardless of whether or not it actually bites harder (which seems is still open to debate?). I don't know about any of you, but I actually opine that the mouths of certain giant macrophagous dinosaurs are up there as some of, if not even the, most potent terrestrial animal weapons in their weight range (those families including allosaurids, carcharodontosaurids, megalosaurids, ceratosaurids, and tyrannosaurids, namely the albertosaurines and bone-crushing tyrannosaurines). I think similarly with regards to the bite of the Komodo dragon and great white shark, though in the aquatic domain in the case of the latter. |
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Post by theropod on Jul 12, 2018 17:04:11 GMT 5
Sadly, no luck with the FE model on my side either. It seems hard to believe that it wouldn’t be part of a scientific paper. But perhaps it’s ongoing research that hasn’t been published yet?
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Post by theropod on Aug 26, 2018 16:05:21 GMT 5
something I’m sure Infinity Blade will find interesting: Bates, K. T., & Falkingham, P. L. 2018. The importance of muscle architecture in biomechanical reconstructions of extinct animals: a case study using Tyrannosaurus rex . Journal of Anatomy. doi:10.1111/joa.12874 onlinelibrary.wiley.com/doi/pdf/10.1111/joa.12874 |
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