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Post by Grey on Jun 7, 2014 3:57:58 GMT 5
One point to clarify, the differences between meg teeth and GWS teeth are IMO more indicative of their respective different hunting/killing style than their similarities.
The main point is that megalodon had teeth more adapted to impact bones than GWS teeth, whales bones with teeth marks from megatoothed sharks are common and the frequency of fossils bones impacted in body regions usually avoided by GWS in cetaceans preys items are rather high. GWS is a more "subtle" killer than megalodon.
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Post by Godzillasaurus on Jun 11, 2014 0:32:03 GMT 5
Are you talking thicker laterally or in terms of its edges? Megalodon's teeth were nonetheless very broadened, but they were still rather thin.
I already realize this: I said it earlier in this thread. I brought it up to explain why livyatan would fare better here than a sperm whale of similar size.
That is true, but I was talking proportionally. Megalodon possessed a roughly comparable tooth length-mouth size ratio as the great white does. Of course its teeth would be much larger in general, but proportionally it was not all that different. That is true though that longer teeth tend to cut less efficiently
I get this, but most cutting teeth do not need to have such a high aptitude for stabbing deeply or crushing. The typical slicing-tooth profile is broadened laterally while being narrow with typical serrations on the edges. It does vary with the type of animal possessing them and the killing style, but they are still very similar and have a specific purpose.
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Post by creature386 on Jun 11, 2014 1:44:04 GMT 5
Are you talking thicker laterally or in terms of its edges? Megalodon's teeth were nonetheless very broadened, but they were still rather thin. Given that large teeth are less than 20 cm long, his numbers have to refer to the edges. Megalodon possessed a roughly comparable tooth length-mouth size ratio as the great white does. Of course its teeth would be much larger in general, but proportionally it was not all that different. That is true though that longer teeth tend to cut less efficiently. This is a greatly oversimplified statement. Grey and theropod had an intense debate on tooth spacing. Even though some scientists assume spacing comparable to the great white in otodontids (like Kent), they had a lot to debate and spacing is one of the many factors that influence this ratio. I don't know if the debate was here or in the thread on megalodon's size, both threads pretty much overlap.
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Post by theropod on Jun 11, 2014 2:14:06 GMT 5
C. megalodon’s teeth are thicker labiolingually as compared to those of great white sharks (their blades are thickened). Individual teeth may not be broader (mesiodistally) relative to the mouth size (that depends on the position), but they are generally broader compared to tooth height and more robust in shape because the anteriors are proportionally shorter. Only very roughly, although they probably both fall into "slicer"-morphospace in that regard. C. megalodon wasn’t just a linearly upscaled great white. Even if it was, allometric developements would surely alter its morphology, and being not that closely related at all doesn’t help. That was not what I’m saying, and it actually isn’t true. It frankly depends on the way they were used. Very long teeth can also cut efficiently, but they require a different biting mode, otheriwse sabretoothed cats would bite exactly the same way as komodo dragons. Stabbing deeply ocurs (e.g. machairodontidae, thylacosmilidae). Crushing, by definition does not, if they are so blunt that they rather crush than, slice they are not slicing teeth any more but rather crushing teeth. that doesn’t mean an animal with such slicing teeth could not on occasion crush something, but the teeth won’t play a role. I take it that you meant to write narrow laterally (even in sharks most teeth tend to be directed like that, although their tooth orientation is rather unusual with the frontal teeth indeed having their carninae more or less pointing laterally) and broadened anteroposteriorly. But it generally makes more sense to use the terms mesiodistal (along the toothrow) and labiolingual (inside/outside of mouth, i.e. perpendicular to toothrow), they are less confusing when talking about oral anatomy baceuse they clearly refer to the mouth and dentition and not the whole animal’s body. creature386: that was on magalodon size, not here.
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Post by Grey on Jun 11, 2014 20:27:57 GMT 5
That one is from South Carolina, belonging to a French collector I'm in contact with and is 5 cm in thickness. That one is from Peru and is 7.5 cm in thickness. Even at parity, that's much more thicker than GWS teeth. Biomechanically, they also acted differently. From Brett : The teeth of megs (and the other otodontids as well) have a rather different tooth morphology than great whites. In particular, their roots have a deeper basal notch which would effectively increase the tenacity with which the collagen fibers hold the teeth to the jaw. In other words, for a meg and great white with the same tooth size, it would take considerably more force to dislodge the meg tooth. This root morphology would seem to be more consistent with a broader jaw shape,or perhaps a narrow jaw shape where the muscles insertion points had migrated slightly closer to the front of the jaws, or bigger jaw closing muscles, or some combination of these possibilities. Certainly, there's evidence that meg had a substantial bite force. Damage to the tips of meg teeth (and an even greater extent in Parotodus) is frequently in the form of compression fractures (the enameloid and dentine at the tip are crushed to powder). This is very different from other macrophagous sharks which almost exclusively have spall fractures (force is applied to one side of the tip which causes a flake to be knocked off the opposite side of the tip). The only other animal I know of with a high frequency of compression fractures is hyenas, which have a VERY high percentage of compression fractures from cracking bones. So somewhere in the interplay of jaw shape, muscle insertion points, and muscle sizes we need a meg jaw that can deliver a devastating bite force. But until we have an actual meg jaw to study in detail we have no way to know how it all played out.
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Post by Godzillasaurus on Jun 13, 2014 7:59:54 GMT 5
It seems like you are talking about longer teeth IN GENERAL (in terms of actual size, not shape or elongation), in which case you are still right. But morphologically, broadened teeth tend to be more efficient at slicing, regardless of whether or not it was recurved or in possession of sharp carinae (at least in the sense of how the great white and supposedly megalodon killed)
No doubt deep penetration will occur (depending on the hunter and the killing style), but simply, for such intense ripping like we see in the great white shark and supposedly megalodon (and for an analogy, many groups of macrophagous theropods), thin-edged but yet broadened (a narrow shape) dentition would be the most ideal. Slenderized dentition would be much less ideal for this kind of killing style (where the actual killing done relies on the intense blood loss, tissue damage, etc) and would instead probably break easily.
As for smilodon and related genera, it would likely have not utilized this killing style. It seems as if, despite the great differences in maxillary canine anatomy, it would have killed similarly to modern felids (and carnivorans that utilize their jaws as their primary killing weapons for that matter) and would NOT be ripping out any musculature or tissue as we would expect from an animal like the great white (at least in the same way). If you do have evidence of this killing style, that would be terrific if you could post it
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Post by theropod on Jun 13, 2014 19:45:03 GMT 5
I am only talking about teeth with sharp carinae, teeth that lack them do not cut. Long teeth can also be good for slicing, but they require unusual adaptions (not the same as in your typical shark, carnosaur or monitor lizard) and that hypertrophy usually only affects a small part of the entire dentition. Slicing teeth generally have a low base ratio (labiolingual width/rostrocaudal lenght of the tooth crown), i.e. they are comparatively long (broad in your terms) and narrow. Crown height is somewhat variable, but it tends to be moderate compared to the (toothrow-)lenght in "saw-jawed" animals.
By comparison in animals that have less emphasis on slicing the teeth tend to become broader (i.e. thicker) in labiolingual direction compared to the rostrocaudal lenght and often also the height, i.e. the crown base ratio is higher, and the tooth thus less compressed, which makes it less effective at cutting but less prone to breaking due to being loaded in multiple directions.
Not necessarily (it depends on its size and proportions), primarily it wouldn’t be so effective at cutting. Having long and narrow crowns aids the cutting action simply because it reduces the edge angle and thus the resistance encountered while cutting. With an equal amount of material, a conical or subconical tooth would be more resistant to loading in various directions, which is why such teeth are usually found in animals that hold onto prey with their mouths while ziphodont teeth are found in animals that slash through their prey. Flat, broad tooth shapes like that of the great white sharp are strong in the direction they are broad in, but susceptible to breaking if loaded in other directions.
I was not saying they killed the same was sharks do, in fact I was explaining why they did not. They definitely did not kill like modern felids. How could an animal with sharp, ziphodont canines possibly kill the same way as one with conical canines that are many times shorter? Machairodontids killed by slicing something. The last thing I heard was that there were multiple theories as to where exactly they bit their prey, but to me it makes most sense that they would go for the neck and sever major veins and arteries. Phantherines and felines kill by puncturing the spinal chord (small prey) or suffocation (large prey), they do not cause much damage to soft tissues because their canines are not designed for it.
Their attack styles must have been superficialy similar, because both certainly relied heavily on grappling ability, but the details as to how they killed their prey are very different (and as we are talking about the teeth and jaws, it is those details that matter).
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Post by Grey on Oct 29, 2014 21:49:28 GMT 5
A scale comparison of various physeteroids teeth specimens (Toscano 2013) with two teeth from C. megalodon from Applegate and Espinosa 1996 Note : the Livyatan tooth is not the largest known based on its width. The partial tooth number 4 is from an unknown physeteroid from Spain maybe similar to Livyatan in size. The meg upper anterior drawing is the Chicago specimen used by Gottfried for its body size estimate.
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Post by theropod on Oct 29, 2014 22:24:42 GMT 5
Gottfried et al. (1996) used UA2, not UA1.
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Post by Grey on Oct 29, 2014 22:35:52 GMT 5
But this is the tooth actually used by them. Note that what Gottfried considers is UA2 is what Shimada considers UA1.
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Post by Grey on Oct 29, 2014 22:37:48 GMT 5
By the way I'm going to bring more info about meg teeth size and Livyatan ecology discussion. And hopefully give a response to sharks/cetaceans thread.
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Post by theropod on Oct 29, 2014 23:01:13 GMT 5
That’s interesting, what is the reason for the difference, and where does Gottfried et al.’s UA1 go in Shimada et al.’s interpretation? I don’t speak Spanish, does Toscano et al. 2013 say it is the same specimen, or does it just happen to have the same height?
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Post by Grey on Oct 29, 2014 23:58:44 GMT 5
I think I've read this distinction in Pimiento's dissertation about Gatun, I'll check it.
No ! I've just put the two comparisons from the two papers (Toscano 2013; Applegate 1996) and put the specimens at scale using the scalebar.
Gottfried referred to the 168 mm tooth as being the one from Applegate and Espinoza chapter, in the book The Great White Sharks by Peter Klimley. That's the same tooth, it's apparently the largest specimen from the Chicago Museum collection.
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Post by Grey on Jun 9, 2015 18:32:38 GMT 5
theropod coherentsheafBasically, you're suspecting Livyatan to have reached a larger size than Physeter and Carcharocles as well ? I still have some reservations about that, and while speaking with various researchers in both fields, Livyatan is only considered to be comparable, if not slightly smaller, than megalodon and the modern sperm whale.
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Post by coherentsheaf on Jun 9, 2015 18:49:55 GMT 5
Not sure, tbh. My current feeling is that Lyv, and Meg are about similar in size and male Physeter is larger or similar. I hopefully will write more about Megalodon size soon, I expect something interesting in the data, but have to test first.
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