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Post by spartan on Apr 24, 2016 6:34:16 GMT 5
Anything on Livyatan's gape?
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Post by Grey on Apr 24, 2016 7:29:27 GMT 5
No but I'd more expect an orca-like gape than a sperm whale-like.
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Post by Grey on May 28, 2016 22:56:52 GMT 5
WHICH ONE HAS THE LARGEST BITE?I'm back again on this question. Being in military duty these times, I don't have the opportunity to investigate this as much as I'd wish. So I let here some informations that one can use. It is clear from the fossil record that Livyatan and Megalodon both possess the largest macroraptorial feeding apparatus from any vertebrate, including pliosaurs (sorry Max Hawthorne). The question, which one has the biggest jaws and the most voluminous bite overall? The goal here would be to predict this, in the most scientific and reliable way that can be done at this stage. I've asked to Dr. S. Godfrey from the Calvert Marine Museum about the size of the mouth in the 11.43 m long skeletal recreation of Megalodon, the closest reconstruction we have of the animal. Godfrey indicated me the upper jaw perimeter from jaw joint to the other is 290 cm, the straight length of the upper dentition is 61 cm and the transverse width behind the most posterior teeth is 107 cm. Sadly he did not inform me about the width of the jaws at the joints. Scaled to a 18 m Megalodon, the upper jaw perimeter would be about 456 cm. Livyatan upper jaw perimeter can be measured from Lambert et al. figures but it depends about where you can measure the joint of the jaws. I've asked blaze and he found an impressive 530 cm of upper jaw perimeter, unsure though of where to place the corner of the jaw. Personnally, I had rather found something about 420 cm. A secondary question would be, since maths ARE NOT my best field, is a greater jaw perimeter automatically means a larger bite or has the bite radius any impact in this ? In short, which one has the largest bite with two secondary questions, which one has the largest jaw perimeter and bite radius ? I'd be interested in the measurements or opinions of theropod, neogeneseamonster, Life, elosha11, tripoliraider1975, stomatopod, spinodontosaurus and others about that.
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Post by theropod on May 29, 2016 0:07:58 GMT 5
I must apologise, being busy at the time I had put your request aside and then forgotten about it. So with a delay, here are my measurements. The preserved portion is scaled to be 270cm long in a straight anteroposterior line (scaling the whole restored outline to 294cm would have it end up slightly too large, as pointed out by blaze a while ago): Upper toothrow length: 286cm Lower toothrow length: 272cm Upper jaw perimeter: 516cm Lower jaw perimeter: 521cm Here are the lines and landmarks I measured: And to answer that question No, jaw perimeter and bite volume or area certainly aren’t interchangeable. Looking at my measurements, the outline I traced for the lower jaw is narrower throughout its entire length and constrains a smaller area, but the edge length is marginally larger than for the upper jaw. But use of the word "radius" in this context doesn’t make sense. Attachments:
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Post by Grey on May 29, 2016 0:33:39 GMT 5
I expected a good work like this frm you.
As for the answer to the main question, overall the bite of Livyatan would appear bigger than an 18 m Carcharocles ? Or at least how would it compared to it ?
I'd wish there would be a ventral view of the CMM Megalodon chondocranium.
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Post by elosha11 on May 29, 2016 2:40:47 GMT 5
Uggh, I just had a very long response that somehow got deleted. Don't have time to redo. But in general, shouldn't the question also be what functional restraints/advantages each animal's jaw structure provided for massive bites? I think jaw shape, gape, tooth structure, and other biological factors are as important as the proposed volume of the animals' jaws. For instance, even if Meg's jaws were smaller by volume, (which is not in any way certain), I would have a hard time believing that the whale could open its jaws as wide as Megalodon, which is estimated to have 75 degree gape, somewhat in line with great whites. As an analogue, I don't believe that orcas can open their mouths as wide as a great whites. A cartilaginous jaw structure not hinged to the head, even if heavily calcified which we can assume for Megalodon, is likely to produce a larger gape than Livytan's.
Many more thoughts, but that's all I can re-create for now.
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Post by theropod on May 29, 2016 19:56:07 GMT 5
elosha11: Certainly agreed, as I commonly point out the size of two jaw apparata that are this different in function is not comparable either. I’m not sure what part of this discussion would even give that idea. Whose estimate? You are implying that you have reliable information on its gape angle, or more likely that of great white sharks? I have been searching for that sort of thing for quite a while now, but have failed thus far. Similarly here, do you have scientific data on this? The same goes for previous talk about sperm whale and orca gapes, everybody is acting as if they knew their gape angles, but where are the sources? That’s a line of inference I cannot really follow. There’s no direct relationship of any sort between the material the jaw is made of, whether it is autostylic or hyostylic, and what angles of aperture the jaw joint itself is capable of. To give you an analogue, birds are famous for their cranial kineticism, their skulls and jaws can bend and deform, similarly to how they’d be if they were made of cartilage. In no way does this imply a capacity for particularly large gape angles at the jaw joint, e.g. a buzzard Buteo buteo is outmatched in that regard by the majority of carnivoran mammals, despite the latters’ completely rigid crania (cf. Lautenschlager 2015 vs Christiansen & Adolfssen 2005). Animals have big gapes when and if they need them, and this argument can be applied to both the whale and the shark. Something else more directly observable from their respective remains; the length of the jaws does not directly affect the gape angle and more than cranial kinesis or histology does, but it has a major effect on the functional gape for a given extension of the joint. I.e., if one animal has longer jaws than the other, that means that its teeth will be further apart for a given gape angle, and hence capable of engulfing a larger girth. There are contexts in which this is relevant, and ones in which it isn’t, just like with gape angle. refs: Christiansen, Per; Adolfssen, Jan S. (2005): Bite forces, canine strength and skull allometry in carnivores (Mammalia, Carnivora). Journal of Zoology 266 (2) pp. 133-151. Lautenschlager, Stephan (2015): Estimating cranial musculoskeletal constraints in theropod dinosaurs. Royal Society Open Science 2 (11): 150495.
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Post by Grey on May 29, 2016 21:49:04 GMT 5
The 75 degrees angle comes from Gottfried 1996, it is reflected in the CMM mount.
Theropod therefore you still predict a 18 m meg would have a more voluminous gulp than Livyatan?
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Post by theropod on May 29, 2016 22:11:32 GMT 5
That might depend on whose version of an 18m megalodon you mean (is it proportioned like a great white?), but either way, I didn’t predict anything so far.
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Post by Grey on May 29, 2016 22:32:44 GMT 5
I tend to stay classical and to use a scaled up version of the CMM mount.
Which would translate into 456 cm of UJP, transverse width at the most posterior teeth about 168 cm and a dentition straight length of 96 cm.
Notably, the upper jaw of the CMM meg appears to be slightly in horseshoe.
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Post by theropod on May 29, 2016 23:11:05 GMT 5
An 18m shark has an estimated ~3.06m of tooth-row-length (Lowry et al. 2009). This gives us an Upper jaw perimeter of ~3.57m if we add the 17% of tooth-free gape that Kent (1999) observed. Alternatively, there are a number of fresh upper jaw perimeters in Mollet et al.’s (1996) dataset (see below), that suggests the perimeter is a mean of 21% of total length, which would give us 3.78m of jaw perimeter. To be fair, these 5 make it look like there was some allometry, so looking only at them I’d get how one might get the idea that jaw size grows disproportionately. However Lowry et al. found only a small amount in the tooth-row length data, and that was using a sample four times the size. So this begs the question whether this is just an artifact of the small sample size (perhaps more likely since the larger sample of dried upper jaw perimeters doesn’t seem to imply positive allometry), or whether sharks get disproportionately longer tooth-free spaces in the backs of their mouths as they grow larger. fujp tl fujp/tl 1 0.838 4.788 0.1750209 2 1.065 5.300 0.2009434 3 1.150 5.360 0.2145522 4 1.220 5.368 0.2272727 5 1.310 5.633 0.2325581 So these are the figures I would use. I can appreciate that we are already at the core of the disagreement here, but that doesn’t prevent answering that question for either scenario. Does anyone know where blaze found the Ct-scan of the GWS jaws? If it has sufficient resolution, it shouldn’t be too difficult to make a ventral-view comparison of the two.
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Post by neogeneseamonster on May 30, 2016 18:31:28 GMT 5
I was too busy doing some schoolworks so I didn't have much time to think about this for a while but it looks like some fresh talk is going on. Anyway, I'm somewhat confused because of some terms. First, does the 'bite volume' means volume of buccal cavity? or volume/surface area of a toothed part? Also, theropod, does the 'jaw area' mentioned in your work refers to the inner(lingual side) area of blue lines?
p.s: Nice work theropod!
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Post by theropod on May 30, 2016 19:36:13 GMT 5
neogeneseamonster: Yes exactly, the area I measured is everything medial of the respective blue lines, the area enclosed by the dentigerous parts of the jaw and the jaw joints. And thanks btw!
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Post by Grey on May 31, 2016 1:02:13 GMT 5
Still no response?
I'm fine with your extrapolation theropod but I consider the scaled up CMM skeleton a reasonnable alternative.
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Post by theropod on Jun 4, 2016 18:00:39 GMT 5
This is a work in progress regarding the question at hand, it should be considered as a preliminary attempt. There are several problems. The first is that, due to insufficient resolution and obscuring by the lower jaw, I cannot discern the end of the tooth-row, making the otherwise best way of scaling it all but useless (I tried this first, guesstimating the end of the tooth-row, but noticed that the largest teeth were ending up over 18cm wide. When correcting for that, I coincided with the version you can see there). So I’ve used the jaw perimeter derived from it to scale the picture (this revises the largest tooth down to a much more reasonable ~15cm width). Also, the jaw is not in plane view here, but seen at slightly anteroventral angle (confer csi.whoi.edu/media/greatwhitesharkhead3D). I don’t know how much of an impact it has, and it is even possible that the perspectivical distortion, making for a proportionately broader jaw, is a better representation for an adult megalodon anyway, but this remains a potential error factor. Finally, this is a juvenile great white shark, but seemingly the only one with even remotely suitable images available. Either way, as of now I’d say this is inconclusive as to whether an 18m megalodon has a larger jaw area than the Livyatan holotype or not.
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