Megalodon vs. Livyatan melvillei

[Grey]

Awaiting for the future publication (some results that I'm unaware of could still occure) I tend to consider them more or less equals in terms of absolute overall physical might, to be cautious if anything should be discovered to radically change anything about or the other or that one would get progressively a massive advantage on the other.

[Grey]

That said, looking to the description of the dentary size of Livyatan, the outline it self is quite less than the sheer perimeter of the rostrum, and the lower jaw is definitely much narrower than delphinids. Skull length is irrelevant in absolute or Physeter beats any one by a long shot.

[theropod]

Skull length is not irrelevant. By this logic, bite volume is irrelevant, or Carcharodon beats Orcinus. There are other factors in both cases that affect the comparison, which we cannot just ignore selectively where this fits our narrative.Carcharodon is outmatched Orcinus. Physeter has no raptorial adaptations, massive bite force or even functional upper dentition, Livyatan does.

Livyatan’s skull is morphologically very similar to an orca’s, and would have a similar bite size at equal skull length, hence we can compare them. Physeter is morphologically completely different, and we cannot even really talk about a "bite size" considering it has no capacity for biting in a manner remotely comparable to the former two.

Inset lower dentition of Livyatan is actually an advantage, the lower and upper teeth not being directly opposed allows the bite to impart higher bending and shear stresses that will make it more effective at crushing (see Meers 2003). This doesn’t make its bite less formidable at similar skull length, if anything it makes it more formidable, but of course it might be hard to see that without acknowledging that bites don’t all function the same way, and that the bite with the largest volume isn’t automatically best in all those aspects.

That being said size of the rostrum still corresponds to the size affected by the bite, unless we propose that the upper teeth all just vanish during biting. I could find no suitable image of a complete orca mandible to compare to Livyatan’s, otherwise I would have done so. However, with the longer tooth row and resulting larger upper jaw bite area in Livyatan compared to Orcinus, I would not be so sure if the bite area of even the mandible alone (as much as I find that rather irrelevant) is smaller than in Orcinus when scaled to equal skull length.

Perhaps Grey wants to provide such a comparison in support of his claims?


Of course since neither of these two is actually optimized for cutting out chunks of flesh, bite volume is not very important for Livyatan/Orcinus to begin with. Length of the jaws is in fact probably the more important measurement, relating to such aspects as the ability to achieve a sufficient gape to achieve a serious bite on an opponent with high girth (such as a white shark or megalodon respectively), and sufficient power in those jaws to clamp onto it firmly.
Clearly, raptorial delphinid skulls are a pretty good analogy for Livyatan here, and if Livyatan at the same size would have a significantly bigger set of jaws (by all measures, not just a single nitpicked one), that’s not "irrelevant".

[Grey]

My point still stands, the outline of the dentary in size is not exactly as wide as thz rostrum itself, hence the bite less wide than in Orcinus (no one said less effective).

Just using skull length without taking into account the differences limit the relevance of it, just like using bite volume is only limited in relevance.

The best advantage of Livyatan is his maneuvrability and ramming ability.

[elosha11]

Without getting into which bite is "best," a rather subjective characterization, I agree that Livyatan's skull length is not irrelevant to bite volume, as volume is obviously increased by greater width and/or length of the jaws. Livyatan does have a very impressive overall bite volume. And I think we can all agree that bite volume is a relevant factor in these animal's overall predatory capabilities. However, as voluminous as Livyatan's jaws are, its lower mandible in particular is far more narrow than that of a Megalodon. Even the widest part of the upper skull is likely more narrow that a large Megalodon's semicircular bite. Now that still may have advantages that the shark's jaws do not naturally provide, as theropod points out, because the whale's jaws are interlocking and can shear and crush very effectively. Still overall, especially when considering the far thinner lower mandible, it seems fairly intuitive that Megalodon had the bigger bite. Of course this also doesn't take into account the gape of the animals. We can infer that Megalodon likely had a wide gape. We don't know about Livyatan. Modern sperm whales seem to have a respectable gape, but nothing extraordinary (and why would they, considering their life style/prey selection). We simply don't know re Livyatan, which was obviously a macropredator unlike Physeter.

As to the comparison of Livyatan's jaw shape and volume to that of an orca, that seems somewhat puzzling. The upper jaws may indeed be "orca-like" but the lower jaws are most certainly not, they are much more akin to Physeter's narrow mandible. On the other hand, Livyatan's teeth seem comparatively large than orcas.
Compare:







To me, Livyatan's jaws seems more of a combination of orca and sperm whale. As to whether Livytan's has comparable jaw volume to orcas, at parity, I'd have to let our more mathematically inclined posters run the appropriate simulations.

[elosha11]

Double post somehow...

[theropod]

Grey The teeth in the maxillae are still there, and still contact the prey, whether or not the lower teeth are placed more medially. This just doesn’t make the bite smaller. As I wrote, the more medial placement of the lower teeth would even likely increase the crushing power, as suggested for Tyrannosaurus, so if anything, it is an advantage.
And of course the point was to get an idea of biting efficiency, I thought that was obvious from the get-go, you have yourself been conflating bite volume with effectiveness of the bite throughout this thread after all.

But at any rate, this is grasping at straws. If you can compare Livyatan and megalodon jaws and conclude the latter’s jaws are larger (I could of course also name ways in which they aren’t if I wanted to nitpick), then I can certainly compare Livyatan jaws and orca or pseudorca jaws (which are far more comparable in shape and function, and where the difference is far clearer) and conclude the former’s are larger for a given body size. This is just not a debatable issue unless we assume the Livyatan holotype was 19 m+ and hence had a relative skull size similar to an orca’s.

[theropod]

Regarding the size of the bite, here is a variation on the scale I already posted a few pages bach, including the area of the mandible.


As I already explained, I found no suitable figure of a complete orca mandible in coronal view to compare this to, which is why it’s not in the original chart (which compares upper jaw to upper jaw in the palatal view), but the area of Livyatan’s dentigerous mandible is still at least as large as the equivalent area in the orca’s upper jaw, so unless orcas have significantly wider lower jaws than upper jaws, if anything it is Livyatan that has the bigger bite at skull length parity.
As I wrote I would encourage people other than me to make comparisons to illustrate their points, if they have the evidence they need to do so. It is easy to make an unsubstantiated claim. If we were all substantiating our claims at the time we are making them, we could save ourselves a lot of time and energy debating irrelevant points.
In this case, it is easy to substantiate that an orca and a Livyatan would have a pretty similar bite size at the same skull length, hence the original comparison, using skull length as a proxy, still stands.

So let’s stop the baseless speculations at this point, and simply accept that Livyatan’s bite is way bigger than delphinids’ would be at the same body size, which I think there can be very little doubt about.


elosha11 :
Of course Livyatan’s rostrum is narrower than the jaws of a large megalodon (but of course, it is also longer).

But I question firstly the relevance of comparing it to a large megalodon in the first place¹ and the relevance of comparing such dimensions among so vastly differently shaped jaw apparata.
And while the bite of a large megalodon would probably be more voluminous as well, which is a more universal basis for comparison, that is also of limited relevance (I’m not saying none, but limited). even if Livyatan had a larger bite volume by having a more semi-circular shaped set of jaws, all other things remaining equal, that wouldn’t make its bite more effective.

At any rate, no matter how you slice it, if we consider the Yorktown dentition to belong to a significantly larger set of jaws than the Livyatan holotype’s, then the jaws of a great white shark will also regularly be larger than those of an orca.

Hence the comparison with Orcinus and Pseudorca, which are obviously far more similar (and how these animals in turn compare to great whites, which is obviously something that is of interest). That Livyatan has a larger jaw apparatus (in volume and all dimensions) than Orcinus, has much clearer implications, it’s not a morphologically disparate structure larger depending on the dimensions you chose (width but not length etc.), it’s a very similar skull larger by every measure.

If you tried to compare a large pliosaur skull to a Tyrannosaurus skull and declare which one is bigger or which bite is more devastating based on their measurements, I think you’d have some serious trouble finding an adequate justification for that, even though of course these jaws have very different dimensions. 
But comparing a smaller pliosaur skull to geometrically similar, but larger pliosaur skull (Pliosaurus vs Liopleurodon) is a no-brainer. Same for Livyatan and an orca. It should be pretty obvious that if Livyatan scaled to the size of an orca has a 1.5 m skull, and the orca just has a 1 m skull, the former has the more formidable set of jaws. Same with Pseudorca. A Pseudorca might just have a 60 cm skull, but Livyatan’s at the same size would be closer to 90 cm. This is strictly about the jaws, of course, but still I cannot see how when making the analogy, this is not important to note.

So from that it follows that
A: If a 5 m orca can bite a 3-4 m great white and hold it in its jaws (Pyle et al. 1999), apparently without problems, then jaws the size of the Livyatan holotype’s could do the same with the Yorktown megalodon, which is similar-sized compared to its jaws. This is not comparing their respective power (postcranium), simply the ability of the jaws to bite and hold onto the opponent/prey item, which is determined by the size of the skull.
B: Even if great whites prey on Pseudorca², that doesn’t translate to this scenario, considering differences such as Livyatan having 50% larger jaws at the same size. Especially if we consider even jaw size differences between such different animals as Livyatan and megalodon important, it is clearly important to note that one animal has vastly larger jaws when those jaws have a similar shape and function.


¹I think I have already given it a fair bit of leeway by using grey’s figure for the Yorktown dentition, which I do think is clearly a large megalodon if we consider the sizes of isolated teeth…as I wrote I would tend to agree to simplify the comparison by only comparing specimens for which a reliable size estimate can be made, but then again, most, if not all, other associated dentitions are actually smaller than that specimen.
²Although of course it has to be noted, again, that there is still not a single recorded instance of successful predation by any shark on Pseudorca. At the very least, this suggests that if great whites do it, they do it with a significant size advantage (e.g. 5.5 m great white vs 4 m Pseudorca), possibly just as large as that of orcas killing great whites.

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[Grey]

I agree the grasp and gripp effiency is increased as well as probably the sustained bite force but still the bite itself, not the rostrum is narrower than orcas or at least not larger. Delphinids have a wide hyoides that physeteroids don't have. This also suggests a slightly different way of killing or food diet.

And I still don't consider the Yorktown meg as a large one as isolated teeth 40-45 % more massive do exist.

The Chilean meg is almost the same size.

So two of the extremely rare meg associated dentitions would come from large specimens ? That is some luck no ? And the Danish centra, rare fossils, is also from a large individual ?

There is a partial set of near 7 inches teeth. So on the few associated sets in the world we would have the luck to have large or very large specimens ?

I will let this thread some time and come back when something new comes which should not take too long.

No, they are as normal as the Livyatan holotype.

[theropod]

Did you even look at the comparison? The bite of Livyatan is way bigger than that of an orca at similar body sizes. If anything, it even appears to be bigger at similar skull length.

Perhaps we need another visualization of that:

This is how an orca skull and Livyatan skull would compare at similar body sizes if Livyatan was approximately 15 m long. If someone thinks the Livyatan here wouldn’t have a bigger bite, they are seriously kidding themselves. And if someone thinks that is not relevant, but thinks the more voluminous bite of megalodon compared to Livyatan is, then they need to seriously rethink at least one of those positions.

What does the hyoid have to do with any of that?

When in 138 teeth, the largest is 13 % taller and 23% wider than the equivalent in the Yorktown dentition, I do consider it a large specimen, yes. That is what isolated teeth imply, if they imply anything.That if you look for the largest in thousands of teeth you can find a few even larger than that is not surprising at all. An 18 m sperm whale is a large specimen too (for an adult bull), but if you look at a few thousand (adult bull) sperm whales you will probably find some individuals larger than it. I know I didn’t look at a few thousand, and I effortlessly found several.

But as I reiterated countless times by now, I am totally fine with ignoring isolated teeth if we cannot agree on the various issues surrounding those. 

Still, the correct way to calculate an average if you have several dentitions is to take the average of those specimens, not pick one that you guess must be average and just forego any testing of that hypothetis despite the availability of data to do so. If we had 5 Livyatan skulls, I wouldn’t pick the largest of those to represent the average, even if I had the impression it isn’t exceptionately gigantic compared to the others. If we want to know the average, we have to calculate the size of each of those, then take the mean.

But instead, we cannot even content ourselves with using the Yorktown megalodon, we need constant hints of bigger specimens from isolated teeth?

[Grey]

The two largest of the dentitions are almost the same size and are adults, all the other, except maybe for the Japanese one, are so much smaller that they are unlikely to represent the same ontogenic stage. Large if you compare to a majority of teeth from young sharks ?
Use the adult isolated teeth in the sample then.
A 10 cm wide meg tooth is a normal large specimen, very much like could represent the Livyatan holotype.

That and the massive but relatively narrower bite is why I consider both roughly equal for now.

[theropod]

Well good, you know very well that the last part is exactly my position, and has been for years. And as you will find I have been using the Yorktown dentition for all manner of comparisons these last few pages, so whether you agree with me that it is a large specimen, or not, you should find all those calculations generous or at least fair towards the shark.

As for megalodon size, do we, or do we not want to consider isolated teeth now?
I didn’t originally calculate an adult average, because I thought you would not appreciate the idea, and you know as well as I do that for any given tooth (except neonates), we cannot conclusively (or independently) tell whether it was from a mature shark or not. Hence why I focused on how relatively few teeth correspond to individuals larger than the Yorktown dentition. It seems pretty clear that those are too few for it to be an average adult, hence why I posted the histogram plots, but of course if you are asking me to do so, I can happily give you a point estimate for adult average size too.

The best (and only thing) we can do is guesstimate a size at maturity by scaling from white sharks.

Average size at maturity in great whites is around 3.66-4.27 m (cited in Cailliet et al. 1985). Mean size of n=652 white sharks as reported by McClain et al. 2015 is 3.81 m. Average for all individual identified as A1-A2 is 12.2 m based on crown width (n=128), 11.9 m based on crown height (n=138), all scaling from your estimate. So if we scale based on that, the mean size at maturity would be 12.7 m and 12.3 m respectively. Before you feel the need to remark on this, I could name you many reasons why this assumption could be off in either direction, perhaps more than you, but it is a middle-point so it is the most objective thing to use.

Crown width hence gives us n=59 adults (42 smaller than yorktown, 17 larger), crown height gives us n=64 adults (55 smaller than yorktown, 9 larger), with respective mean adult sizes of 16.0 and 15.3 m. (But see below)

mean size at maturity in blue, mean size of adults in green, size of yorktown dentition in red

If something is larger than 7 to 9 in every 10 adult specimens, I consider that something to be large for its species. Not extreme (we have a few examples of teeth that probably fit that term better), but not average or typical either. That is only based on isolated teeth, of course. Yet I keep reading references to teeth that are larger, but never to the much bigger number of teeth that are smaller, why is that?

are so much smaller that they are unlikely to represent the same ontogenic stage.

Do you not see the circularity here? The dentition is a normal individual? Why? Because other individuals are similar in size, if we ignore individuals that are smaller because we assume they are less mature, because they are smaller?

But we consider the Livyatan holotype (likely a young adult based on open pulp cavities and little tooth wear), then why would we not consider a 15-something metre meg, like the one represented by the boneclones dentition (unless you are saying a 15 m meg would not be an adult at all?).

Anyway, irrespective of whether you agree or totally disagree with any of what I wrote up until this point (not to say that most of it is really up for debate), can we at least agree about the simple fact that the average of a sample is calculated as just that, the average of the sample, and not "random observation in a sample that one personally thinks seems to be average"?
Even if Uyeno et al.’s or the Chilean specimen are just slightly smaller than Yorktown, the average is the mean of those specimens (and arguably the shark listed on boneclones, not an officially available, publicly housed specimen, but then, neither are any of the others, except for Uyeno et al.).

Cailliet, G.M., Natanson, L.J., Welden, B.A. and Ebert, D.A. 1985. Preliminary studies on the age and growth of the white shark, Carcharodon carcharias, using vertebral bands. Memoirs of the Southern California Academy of Sciences 9 (4): 49–60.
McClain, C.R., Balk, M.A., Benfield, M.C., Branch, T.A., Chen, C., Cosgrove, J., Dove, A.D., Gaskins, L.C., Helm, R.R. and Hochberg, F.G. 2015. Sizing ocean giants: patterns of intraspecific size variation in marine megafauna. PeerJ 3: e715.
Pimiento, C. and Balk, M.A. 2015. Body-size trends of the extinct giant shark Carcharocles megalodon: a deep-time perspective on marine apex predators. Paleobiology 41 (3): 479–490.


PS:
Ratio of all tooth widths in Pimiento & Balk’s sample and the mean of teeth of same assigned range of positions in the Yorktown dentition:


(vertical line is mean size at maturity scaled from great whites)

Mean of entire sample (n=512) 0.650 × Yorktown (11.1 m)
Mean size at maturity based on McClain et al.’s and Caillet et al.’s figures for great whites: 0.676 × Yorktown (11.6 m)
Mean size of adults (individuals >= 0.676 × Yorktown, n=223): 0.865 × Yorktown =  14.8 m

So based on the estimates derived from the tooth widths of all 512 teeth in the original dataset that had crown width measurements available, the average adult megalodon is a little under 15 m long based on the Yorktown specimen (using the size suggested for it by grey).

[theropod]

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[prehistorican]

What would be the maximum if the average you calculated is 14.8m?

[theropod]

The largest individual in the dataset would be CP 6, a lower anterior (a1) from the Messinian of Chile (Bahia Inglesa Fm.) with a crown width of 105.89 mm, 1.253 times the same measurement (84.5 mm) in the Yorktown dentition.