Megalodon size

[theropod]

What an enourmous whale shark. It would be so amazing to swim with one of those.

But surprisingly light, a megalodon of the same lenght would be more than twice the weight. How come it only weighs 34t?

@size issue: How does he explain the presence of Livyatan, giant Pliosaurs and Ichthyosaurs?

[Grey]

Kent regarding the whale shark body mass :




Regarding size issue, he only quotes McHenry. Most marine carnivores topped at around 10 tonnes, with one individual of P. macromerus certainly approaching 20 tonnes. McHenry cites 10 tonnes as the usual benchmark for size in top carnivores, with limited examples, representing large or old individuals topping at 20 tonnes. When they cite 10 tonnes, think more about 10-20 tonnes as an usual maximum range. The only ichthyosaur known to have certainly exceeded 20 tonnes is the 21 m TL, teuthivorous S. sikanniensis (that McHenry estimates at around 40-50 tonnes), just like the teuthivorous Physeter. No precise size estimate has been made for the giants predatory ichthyosaurs known by a few teeth and fragments and they could fall in the range of the largest pliosaurs.
Livyatan was described after McHenry's dissertation, I talked about it in my mail to Kent. There is no strict body mass estimate for it, even though it is pretty certain it may have clearly exceeded the 20 tonnes mark. However, just like for the contemporary meg, the extraordinary size of Livyatan, for an amniote top carnivore, is related to the diversification of whales. Their respective cases are similar, they were specialized on the largest known marine preys ever. Only, Kent expects on theoretical grounds meg to reach larger sizes than predatory amniotes because of its cartilaginous skeleton. However, he expects too that the largest megs were not particularly efficient as active hunters because of their relatively simple and less efficient cardiovascular system. In anycase, Livyatan and meg are unique, due to their specific evolution with their preys. If whales had not evolved, it doesn't seem that a predatory shark and a predatory whale such as meg and Livyatan respectively would have evolved that big, and as far as we know, since the beginning of evolution it had never happened prior to their occurrence during the Miocene.

[theropod]

The "usual maximum range" (with the stress on the "usual") already sounds much better.

There is a size estimate for those ichthyosaurs, several remains have been estimated at 14, 15 and 16m, I can send you the paper if you want. Himalayasaurus has been esimated roughly at >15m, which is also supported by the remains (ironically that's also the consensual figure for the megatooth). These are very big animals, just how big has to be further examined by means of weight estimates. Don't count them out so quickly!

The question is, if the large size of megalodon is related to its cartilaginous skeleton, how come other marine vertebrates with bony skeletons can attain similar sizes (Livyatan) or in the case of baleen whales significantly larger ones?

If bone was too costly to built, we wouldn't see giant animals with bony skeletons being far more numerous than those with a cartilaginous one. But for some reason both raptorial predators having cartilaginous and bony skeletons attained comparable sizes during the same period.

Probably the advantages of bone (sturdiness, vascularization, calcium storage) can easily make up for its greater physiological cost, which is why most giant organisms have developed a bony skeleton, with the notable exceptions of sharks and placoderms.

Most likely, this isn't actually related to the cartilage but rather to the bauplan of chondrichthyans in general being better suited for attaining large sizes than that of actinopterygians (again, with some exceptions of the latter also becoming very big, like Leedsichthys problematicus)

The "uniqueness" of the cetacean diversification as regards food sources for big predators is at best debatable too, but we already had that discussion so we shouldn't start it again.

Concerning the weight of that Rhinconodon typus:

"the piecemeal weight is usually about 6% less than the true body weight."
svpow.com/2008/05/20/sv-pow-showdown-sauropods-vs-whales/

This is at least the case for whales. I don't see a shark loosing a significantly greater amount than a whale would. So the weight is still oddly low (~36t), even with all those factors accounted for it would probably be below 40t (given it was actually weighed correctly).

[Grey]

Regarding Rhincondon's weight, Kent doesn't talk about the body cut in pieces as the only reason for that low body mass, read it again.

The question is, if the large size of megalodon is related to its cartilaginous skeleton, how come other marine vertebrates with bony skeletons can attain similar sizes (Livyatan) or in the case of baleen whales significantly larger ones?

If there were biomechanical constrains on the bony skeleton that don't allow for such sizes, we wouldn't see them. If bone was too costly to built, we wouldn't either. But for some reason both raptorial predators having cartilaginous and bony skeletons attained comparable sizes during the same period.

There is a size estimate for those ichthyosaurs, several remains have been estimated at 14, 15 and 16m, I can send you the paper if you want.

There is only Livyatan reaching sizes perhaps comparable to C. megalodon. No other hypercarnivore really reach comparable sizes. Which doesn't mean there can't be some exceptions (undescribed particularly large ichthyosaurs or pliosaurs specimens), which is unclear at now. We are talking about the usual limits in active giants carnivores, it has already been explained how planktonivorous and teuthivorous organisms, bony or cartilaginous have attained even larger sizes (cf : McHenry 2002 mail). Cephalopods and planktoon are an infinitely more abundant and reliable food source than large preys, thus it is easier to reach giants size, whatever the skeleton. The question here is focused on the active marine macrophagous hunters only.

Plus, these estimates for these ichthyosaurs are still vague, the indicator here is the body mass range and these ichthyosaurs could fall in the body mass range of pliosaurs depending their exact proportions.
Even if they exceeded 20-30 tonnes, the general patterns doesn't reject that possibility. But you need specialization on giants preys, like meg and Livyatan, to get really gigantic sizes well above 20 tonnes. No pliosaurs or ichthyosaurs that we know of were gigantophagous specialists. But we are not talking about strict natural rules, but general patterns.

The uniqueness of the cetacean diversification as regards food sources for big predators is at best debatable too, but we already had that discussion so we shouldn't start it again

.


Why debattable ? For both meg and Livyatan, this has been proposed as the main reason of their evolution. Coincidentally, at the same time and both reaching larger sizes than any known marine reptile or predatory fish known before. My mail to Kent was in that way asking him if there was another reason for such a in a shark such as megalodon (which is totally extraordinary as no other macrophagous fish ever even approached such proportions), other than whale evolution. But it seems this is the only valid and proposed explanation. There's no debate here. There can be others reasons why they got that large but no other strong proposition has been made for them.

[creature386]

Aug 1, 2013 17:20:51 GMT 5 Grey said:

There are very few found.

The largest published was 230 mm found in Denmark in 1983 with 19 others vertebras and one associated upper anterior tooth (about 16 cm high and 12 cm wide). Since this is only the largest of the 20 associated, and that according to Gottfried et al. meg had around 200 vertebras, this is perhaps not the largest in this particular individual.

Source : "Carcharodon megalodon from the Upper Miocene of Denmark".

There is also a vertebral column found in Belgium. From what I remember, the specimen was less than 10 m long. Gottfried mentioned it in his paper.

[Grey]

Aug 3, 2013 19:09:23 GMT 5 creature386 said:

Aug 1, 2013 17:20:51 GMT 5 Grey said:

There are very few found.

The largest published was 230 mm found in Denmark in 1983 with 19 others vertebras and one associated upper anterior tooth (about 16 cm high and 12 cm wide). Since this is only the largest of the 20 associated, and that according to Gottfried et al. meg had around 200 vertebras, this is perhaps not the largest in this particular individual.

Source : "Carcharodon megalodon from the Upper Miocene of Denmark".

There is also a vertebral column found in
Belgium. From what I remember, the specimen was less than 10 m long. Gottfried mentioned it in his paper.

I know, however to my knowledge, the mount was made of unassociated vertebras found in verious regions of Belgium. They've removed it, I guess it is in the archives of the museum at now. So bad, this one is not under further study.

[creature386]

Gottfried only mentioned a region in the near of Antwerp, when talking about the location where it was found.

[Grey]

Aug 3, 2013 19:29:23 GMT 5 creature386 said:

Gottfried only mentioned a region in the near of Antwerp, when talking about the location where it was found.

I know but that's contradictorial with my contacts in Belgium who said that it was composed of originally unassociated pieces. Whatever it was a beautiful specimen.

[theropod]

Regarding Rhincondon's weight, Kent doesn't talk about the body cut in pieces as the only reason for that low body mass, read it again.

Would you say this would have greater impact than the piecemeal-weighing method (assuming that was done; animals up to 53t have been weighed in one piece)? Otherwise even then it remains oddly light. What weight would you predict for a whale shark that lenght?

There is only Livyatan reaching sizes perhaps comparable to C. megalodon.

But others, known from smaller samples, clearly in excess of 10, and some perhaps even 20t.
And some whose weight is an unknown figure, because nobody has taken great interest in it, but which can nonetheless be expected to be gigantic. This is not something you can just deny.

I think you are just too reluctant to accept anything perhaps challenging the "champion"(s).

How rare this is...of course huge predators are something that doesn't occur all the time. Very likely on average throughout evolution raptorial predators were below 10t (like for example in todays oceans, however I think in this case it's just for the time until a predator able to tackle prey in artic waters supersizes again, since there are still lots of huge whales around to feed such an animal). In this regard, I'm completely agreed with that assertion.

Im not agreed once this is interpreted as "raptorial predators above 10t are an absolute rarity and ones above 20t only occured on one single occasion", and I don't think calling this some kind of "limit" is appropriate. Even the scarce evidence we have to date makes this seem unlikely, with several candidates of mesozoic marine reptiles presumably in excess of that proposed benchmark.

No other hypercarnivore really reach comparable sizes. Which doesn't mean there can't be some exceptions (undescribed particularly large ichthyosaurs or pliosaurs specimens), which is unclear at now. We are talking about the usual limits in active giants carnivores, it has already been explained how planktonivorous and teuthivorous organisms, bony or cartilaginous have attained even larger sizes (cf : McHenry 2002 mail). Cephalopods and planktoon are an infinitely more abundant and reliable food source than large preys, thus it is easier to reach giants size, whatever the skeleton. The question here is focused on the active marine macrophagous hunters only.

That those had enough prey during the Miocene however means this is possible in other epochs too.

Plus, these estimates for these ichthyosaurs are still vague, the indicator here is the body mass range and these ichthyosaurs could fall in the body mass range of pliosaurs depending their exact proportions.
Even if they exceeded 20-30 tonnes, the general patterns doesn't reject that possibility.

Plus, these estimates for these ichthyosaurs are still vague, the indicator here is the body mass range and these ichthyosaurs could fall in the body mass range of pliosaurs depending their exact proportions.

Or they could fall within the size range of large adult C. megalodon. "Could" is generally not a very useful phrase in such scenarios.

You should be happy, the estimates we are talking about are not equivocal in the slightest, so no need to presume that they are and may be corrected downward.

Even if they exceeded 20-30 tonnes, the general patterns doesn't reject that possibility.

I have no problem with a general pattern that holds true for most animals, but with the suggestion of that pattern being obligatory for all but one, geologically pretty short time period, that one being in some way not comparable to any other epoch in evolution.

But you need specialization on giants preys, like meg and Livyatan, to get really gigantic sizes well above 20 tonnes.

No, rather quite the opposite by your arguments.

First of all, as you yourself highlighted, Livyatan is probably not a gigantophagous taxon, at least not lone individuals. you have even shown a quote suggesting that.
Secondly, you are contradicting yourself; on the one hand, you argue (or agree with that or whatever) giant predators were usually theuti- or planktivorous (undoubtedly specialization towards small to tiny prey or even micropredatory), and on the other hand that to get really huge as a predator you would have to predate on giant prey (while your two examples are likely not both gigantophagous and yet of similar size).

Like pliosaurs, Livyatan or Orcinus, an oppurtunistic diet incorporating more or less large animals (and not necessarily giant ones, as in the case of my examples) is fully probable for these ichthyosaurs, as also proposed for Pliosaurs. Giant prey items don't usually contribute a big part of the diet (see Varanus komodoensis as an example of an animal particularly apt at gigantophagy and yet not taking water buffalo on a daily basis), even if the animal is gigantophagous.

No pliosaurs or ichthyosaurs that we know of were gigantophagous specialists. But we are not talking about strict natural rules, but general patterns.

neither is Livyatan, neither is gigantophagy required for attaining giant sizes as a predator. See my above argument

By your logic, T. rex would definitely have to be much smaller than Allosaurus fragilis, since it wasn't a "gigantophagous specialist" (or rather, a non-gigantophagous specialist), no?

Why debattable ?

That this event was unique in prehistory. Should be self explaining

If such a supposedly unique faunal radiation happened once, comparable radiations also happened earlier, and will happen in the future. Other periods just happen to be less well-studied or impractical to study (eg. fragmentary and enigmatic nature of Leedsichthys fossils as well as large marine reptiles), while some receive more attention.

For both meg and Livyatan, this has been proposed as the main reason of their evolution.

What is being proposed does not necessarily have a lot of factual basis, but you have to decide for yourself how feasible you find it.

It's undoubtedly an important reason that the prey was abundant, that doesn't mean there was no abundant prey in other periods.

Coincidentally, at the same time and both reaching larger sizes than any known marine reptile or predatory fish known before. My mail to Kent was in that way asking him if there was another reason for such a in a shark such as megalodon (which is totally extraordinary as no other [known] macrophagous fish ever even approached such proportions), other than whale evolution. But it seems [to me] this is the only valid and proposed explanation. There's no debate here. There can be others reasons why they got that large but no other strong proposition has been made for them.

I think the highlighted ones are the points you have to think about more.

Evolutionary circumstances allowed sharks to radiate during the cenozoic, arguably more so than while they were still supressed or rivaled by marine reptiles (Brachaucheniids, later mosasaurs) and/or subject to mass extinctions (C/T event, pun intended), all major problems in evolving giant size. Newly evolving cetaceans (eg. Basilosaurus) happened to be unsuccessful in taking over permanently (unsuccessful attempts to take over some nich permanently for sure happen often throughout evolution). There can be a huge amount of reasons for that; perhaps they were simply not efficient enough as aquatic predators at that time.
The Miocene radiation of Baleen whales caused a tremendously rich fauna to evolve, there is no doubt. That meant there was enough prey for the predators that happened to be in charge at the time, sharks (which are luckily well-equipped for gigantophagy), to supersize, and similarly huge raptorial whales to evolve. But that doesn't automatically make it the only comparable event in the history of the planet.

Who knows how previous radiations of the marine fauna influenced the predators? None of these are even close to being as well-documented or having such huge sample sizes, and at the same time fragmentary remains possibly indicative of larger sizes are ignored in your considerations.

The most likely thing is that throughout evolution periods of prey and predator radiation and consequently increased body sizes occurred. The oxford clay is an example, as is the Liassic part of the Jurassic coast, as is probably the Anisian-Carnian. The lines of separation between those biota seem far more blurred than you think, differences can mostly be attributed to differences in study, samples and preservation of the remains.

Gigantic prey items (stress on gigantic, in the sense of as big or even significantly bigger than the predator itself) in an ecosystem are not obligatory for evolution of big predators. There are no recorded periods in prehistory, possibly except for the Pliocene, where we know prey animals significantly outsizing the biggest indicated predators. Why is this? for once, out view of extinct ecosystems is always incomplete, and secondly, it is not very typical for lone marine predators to have prey bigger than themselves.

The other reasons "why they got that large" are likely an array of evolutionary circumstances besides the cetacean radiation and to some degree preservation, collection, study and figure bias.

[Grey]

Would you say this would have greater impact than the piecemeal-weighing method (assuming that was done; animals up to 53t have been weighed in one piece)? Otherwise even then it remains oddly light. What weight would you predict for a whale shark that lenght?

Combination of the factors given by Kent in his explanation could, at the same time, resulted in an especially light weight specimen and a massie underestimate of its body mass. If you checked the datas on Mollet website, you could notice that for similar sized sharks (in length) the weights can show a huge disparity.

Also, this 20 m whale shark is not verified, Compagno and Kent stated it as a possibility.

But others clearly in excess of 10 or perhaps even 20t

The only pliosaur approaching 20 tonnes with certainity if the largest individual of P. macromerus. Others large certified pliosaurs are in the vicinity of the ~10 tonnes mark. That's a pattern common in others species. There's no weight estimates for the largest unidentifed ichthyosaurs as we ignore their exact proportions.

That those had enough prey during the Miocene however means this is possible in other epochs too.

Enough preys and enoughly large preys. That's possible others vast food sources composed of very large preys are unknown, but you enter in the realm of the speculation, here again.

Mysticetes generas were four times more diversified and numerous during Miocene than today. If you know another era with a such population of very large preys, tell me.

No, quite the opposite.

First of all, as you yourself highlighted, Livyatan is probably not a gigantophagous taxon, at least not lone individuals.


Like pliosaurs, Livyatan or Orcinus, an oppurtunistic diet incorporating more or less large animals (and not necessarily giant ones) is fully probable for these ichthyosaurs. Giant prey items don't usually contribute a bit part of the diet (see Varanus komodoensis as an example), even if the animal is gigantophagous.

At first, where did I say Livyatan was not a gigantophagous species ? I only suggested (like Kent) that it may have had perhaps different food sources than meg, which does not mean it wasn't gigantophagous at all. So far, its presumed food sources remains whales. And its occurence has been explained by Lambert et al. because of the occurence and diversity of Mysticetes.

If you disagree with that, you disagree with McHenry, Kent (the occurence of meg) and Lambert et al. (the occurence of Livyatan and meg).

These ichthyosaurs are large but, you or I, we don't know their exact size, the reason of their occurence and their preys. I personnally suspect they were in the usual size range of the large pliosaurs and were not gigantophagous specialists.

Now, look closely at the observations by McHenry and Kent, Livyatan and meg are way larger than any pliosaur, mosasaur known or ichthyosaurs known, and have evolved because the whales diversified and increased in size.

Secondly, you are contradicting yourself; on the one hand, you claim giant predators were usually theuti- or planktivorous (undoubtedly spacialization towards small to tiny prey or even micropredatory), and on the other hand that to get really huge as a predator you would have to predate on giant prey (while your two examples are likely not both gigantophagous and yet of similar size).

We are focusing on large active macrophagous predators. Theutivorous and planktonivorous rely on preys infinitely much more available and reliable which explains their ability to easily reach giants size.

neither is Livyatan, neither is gigantophagy required for attaining giant sizes as a predator. See my above argument

By your logic, T. rex would definitely have to be much smaller than Allosaurus fragilis, no?

Livyatan is presumed to have fed on whales and to have evolved because of whales evolutions (Lambert et al.)

Please don't start to bring your beloved theropods on that field. Terrestrial and oceanic predators rely on different variable. And T. rex had preys potentially much heavier than itself.

That this event was unique in prehistory. Should be self explaining

If such a supposedly unique faunal radiation happened once, comparable radiations also happened earlier, and will happen in the future. Other periods just happen to be less well-studied or impractical to study (eg. fragmentary and enigmatic nature of Leedsichthys fossils as well as large marine reptiles)

It is unique in prehistory because of the unique occurence of large mysticetes. I acknowledge that others eras are less studied, but nothing indicates something comparable to what has been seen during Miocene. Leedsichthys is known by more than 70 specimens, and McHenry thinks unlikely pliosaurs were gigantophagous specialists. Regarding the marine reptiles, nothing indicates a similar trend between large preys and large predators just like during Miocene-Pliocene. I am opened to any surprise, but nothing points toward this at now. You're speculating.

What is being proposed does not necessarily have a lot of factual basis, but you have to decide for yourself how feasible you find it.

And you have not proposed something else better. To my knowledge, the occurence of Livyatan because of whale's evolution has not been criticized by futhers studies to now. And I don't give a heck of the skepticism of theropod.

I think the highlighted ones are the points you have to think about more.

Don't give me lessons about what I have to think about. I rely on the observations by McHenry and Kent about the general patterns seen in oceanic top carnivores that's all.

And don't modify my quotes, that's very taipan-like.


Now, I advise you to discuss these questions with Kent or McHenry themselves (and even Lambert et al. since you claim that Livyatan's occurence was not because of mysticete evolution). I only rely on their works so don't bust my balls with your haughty attitude to argue and discuss anything that doesn't please you.

[theropod]

Also, this 20 m whale shark is not verified, Compagno and Kent stated it as a possibility.

Ok, that makes sense then, it sounded as if it was confirmed.

I did check the data on elasmollet, I even derived an "average" weight for a 5m GWS based on the large sharks there. Yes, they show huge disparities, no question. Is this also the case with whale sharks?

The only pliosaur approaching 20 tonnes with certainity if the largest individual of P. macromerus. Others large certified pliosaurs are in the vicinity of the ~10 tonnes mark. That's a pattern common in others species. There's no weight estimates for the largest unidentifed ichthyosaurs as we ignore their exact proportions.

I don't understand your point with "as we ignore their exact proportions"

Enough preys and enoughly large preys.

Most whales during the miocene wheren't that large, neither did predators mostly (or in Livyatan's case perhaps at all) prey on large prey. And yet the predators grew huge.

That's possible others vast food sources composed of very large preys are unknown, but you enter in the realm of the speculation, here again.

Which is a good thing, if not necessary to do in paleontology-within realistic borders

Mysticetes generas were four times more diversified and numerous during Miocene than today.

I wonder where and how that figure was calculated.

If you know another era with a such population of very large preys, tell me.

Since that figure must be derived based on application of a fair amount of speculation, that is, "how large is the portion of the actual fauna represented on the fossil record?", that's not a problem and many time periods are possible contenders.

At first, where did I say Livyatan was not a gigantophagous species ? I only suggested (like Kent) that it may have had perhaps different food sources than meg, which does not mean it wasn't gigantophagous at all.

It was suggested (in it's description, and by its morphology as well as contemporary whale species) that it preyed on mid-siozued baleen whales, certainly nothing bigger than itself.

So far, its presumed food sources remains whales.

Gigantophagy is about relative sizes. Sure, whales are big, but only few whales are actually gigantic relative to Livyatan.
Carcharocles on the other hand probably did prey on whale species even bigger than itself later (B. sibbaldina). Funny enough, it wasn't gigantophagous during Miocene either, at least not as far as we know.

And its occurence has been explained by Lambert et al. because of the occurence and diversity of Mysticetes.

I have no problem with that. Of course a predator occurs because its prey occurs.

If you disagree with that, you disagree with McHenry, Kent (the occurence of meg) and Lambert et al. (the occurence of Livyatan and meg).

Even if, that would be not such a fundamental problem.

These ichthyosaurs are large but, you or I, we don't know their exact size, the reason of their occurence and their preys. I personnally suspect they were in the usual size range of the large pliosaurs and were not gigantophagous specialists.

I doubt the former and fully agree with the latter. They don't have to be giganthophagous specialists to be huge tough.

Now, look closely at the observations by McHenry and Kent, Livyatan and meg are way larger than any pliosaur, mosasaur known or ichthyosaurs known, and have evolved because the whales diversified and increased in size.

The latter is among the factors enabling their gigantism, yes.

Again, it is the "known" that's important here. Besides, the case of the giant ichthyosaurs like Temnodontosauridae sp. and Himalayasaurus is far from being as clear as you think.

We are focusing on large active macrophagous predators. Theutivorous and planktonivorous rely on preys infinitely much more available and reliable which explains their ability to easily reach giants size.

The same can be said about a raptorial predator hunting smaller prey items. Those are abundant too. Both orcas and Great whites primarily hunt relatively small animals (seals and penguins) and still grow very large relative to their prey.

Livyatan is presumed to have fed on whales and to have evolved because of whales evolutions (Lambert et al.)

We propose that Leviathan fed mostly on high-energy content medium-size baleen whales.

No indication of gigantophagy in there.

Please don't start to bring your beloved theropods on that field. Terrestrial and oceanic predators rely on different variable. And T. rex had preys potentially much heavier than itself.

T. rex is evidently not a "gigantophagous specialist", this is widely agreed upon, reflected by its ecosystem and its morphology.

It is unique in prehistory because of the unique occurence of large mysticetes.

Then the upper cretaceous is jsut as unique, because of the unique occurrence of large plesiosauroideans.

Leedsichthys is known by more than 70 specimens, and McHenry thinks unlikely pliosaurs were gigantophagous specialists.

Well then I don't see why you think there was comparatively little prey available during that time; and that despite the preservation of that taxon being evidently problematic...

Again, Gigantophagy is not required. Predators could and can obviously get huge based on a generalist diet

Regarding the marine reptiles, nothing indicates a similar trend between large preys and large predators just like during Miocene-Pliocene.

You have given the answer why this is the case yourself, such trends are not being studied as extensively, neither are you inquiring about them.

but the presence of big pachycormid fish and giant pliosaurs in the same strata is already a correlation.

And you have not proposed something else better. To my knowledge, the occurence of Livyatan because of whale's evolution has not been criticized by futhers studies to now. And I don't give a heck of the skepticism of theropod.

Perhaps if instead of telling me how worthless it is, you could actually properly read and consider my arguments and see whether they are valid.

Don't give me lessons about what I have to think about. I rely on the observations by McHenry and Kent about the general patterns seen in oceanic top carnivores that's all.

And don't modify my quotes, that's very taipan-like.

"General patterns", yes, so don't hypothetise them into obligatory rules that have one single exception.

Now, I advise you to discuss these questions with Kent or McHenry themselves (and even Lambert et al. since you claim that Livyatan's occurence was not because of mysticete evolution). I only rely on their works so don't bust my balls with your haughty attitude to argue and discuss anything that doesn't please you.

NOTE: Provocative and/or agressive statements have been highlighted in red in the quotes.
That this kind of visualisation deeply disturbs you is not my fault, but sometimes it is the only elegant way to show you what you are imo forgetting about. I'm not modifying your quotes and making them look as if they were your original text. I'm making very obvious highlightings and additions to demonstrate my point. If you dislike this so much, I'll try to find another way, if you in exchange stop your provocations.

You shouldn't be complaining, since it's not me who is still posting in an aggressive manner even tough he's containing himself. I try to make a logical point you interpret as in fundamental disagreement with your science, you attack me in a personal manner. It is always the same.

[Grey]

I don't understand your point with "as we ignore their exact proportions"

Ichthyosaurs have been subjected to various revisions about their proportions and body mass. 14-16 m ichthyosaurs could be not that heavy (and 14-16 m are initial estimates).

Without further data, I won't speculate and talk about them like you like to do with almost totally unknown taxas.

Most whales during the miocene wheren't that large, neither did predators mostly (or in Livyatan's case perhaps at all) prey on large prey. And yet the predators grew huge.

They were already on average significantly heavier and bulkier than Jurassic plesiosaurs and ichthyosaurs. The largest Miocene cetotherid is 13 m. De Muizon stated that larger mysticetes occured during Miocene but they were still not common.
Also, they were EXTREMLY widespread and numerous. And at the end, meg, (and presumably Livyatan) specialized on them and grew to immenses sizes. I HIGHLY doubt these macrophagous ichthyosaurs were as big as Livyatan.

Which is a good thing, if not necessary to do in paleontology-within realistic borders

No, I don't speculate, speculations created 150 tonnes plesiosaurs. Nuff said, not my problem if you like it. I rely on hard datas and observations.

I wonder where and how that figure was calculated.

There are sources about it in some wikis articles. I had read the paper, but I don't have the source at the hand. Do your own research work, that's better than speculations.

Since that figure must be derived based on application of a fair amount of speculation, that is, "how large is the portion of the actual fauna represented on the fossil record?", that's not a problem and many time periods are possible contenders.

In short, you cannot found me an era with an oceanic diversity of large multi-tons potential preys, with specialized predators.

It was suggested (in it's description, and by its morphology as well as contemporary whale species) that it preyed on mid-siozued baleen whales, certainly nothing bigger than itself.

Here, we come to something difficult, the definition of gigantophagy. Livyatan is described to have been specialized on whales in its description and is compared to whales. Does that mean that gigantophagy is not appliable or has it to be restricted to meg (understood to have preyed on as large or larger preys then itself) ?

Whatever the term, Livyatan and meg are strongly suggested to have evolved because of the evolution and diversification of whales.

Large macrophagous reptiles of the Mesozoic were not specialized on such a vast source of such large preys.

Gigantophagy is about relative sizes. Sure, whales are big, but only few whales are actually gigantic relative to Livyatan.
Carcharocles on the other hand probably did prey on whale species even bigger than itself later (B. sibbaldina). Funny enough, it wasn't gigantophagous during Miocene either, at least not as far as we know.

I agree on that though.

But the problem is that many whales are still undescribed from Miocene (a new species is going to be published very soon), and I've seen pictures of LARGE skeletons dating back this epoch. Also, the largest cetotherid, at 13 m, is not small at all.

But whatever the gigantophagy's definition, meg and Liv were specialized and evolved to hunt on these particularly large preys, large (multi-tons animals), very abundant and very numerous, and very energetically productive in terms of feeding.

Nothing comparable with the Mesozoic oceanic environments.

I doubt the former and fully agree with the latter. They don't have to be giganthophagous specialists to be huge tough.

Specialization on very large preys favors to reach very large sizes.
You expect them bigger than pliosaurs because you tend to favor optimistic estimates. Since pliosaurs are restricted to 10-20 tonnes as Mesozoic predatory reptilians champions, you slowly try to induce these ichthyosaurs, almost totally unknown, to be the new bigger champions. So theropodish.

The latter is among the factors enabling their gigantism, yes.

Again, it is the "known" that's important here. Besides, the case of the giant ichthyosaurs like Temnodontosauridae sp. and Himalayasaurus is far from being as clear as you think.

I have the repeat myself AGAIN :

- Mchenry, Kent, or I, have never argued that the occurence of a gigantic predator approaching Liv or meg proportions is impossible. Only this does not change at all the general patterns observed by McHenry. Also, perhaps these predators could themselves be highly specialized in some large unknown preys. Sadky, here again we enter in the speculation realm. That's your business, not mine.

- Yes, their cases are FAR from being clear, understand, don't make them already giants badass predators as big as Liv or meg, when you honestly can't. But I have no hope on that...

The same can be said about a raptorial predator hunting smaller prey items. Those are abundant too. Both orcas and Great whites primarily hunt relatively small animals (seals and penguins) and still grow very large relative to their prey.

Orcas prey on the largest marine creatures in the seas, and great whites can prey on large bull elephant seals and pilot whales. Irrelevant.

T. rex is evidently not a "gigantophagous specialist", this is widely agreed upon, reflected by its ecosystem and its morphology.

Let's stay on the size patterns oceanic patterns observed by McHenry, and not you personnal hate toward Tyrannosaurus.

Then the upper cretaceous is jsut as unique, because of the unique occurrence of large plesiosauroideans.

Do they were as numerous and diversified as mysticetes generas ?

And had them specialized predators ? No. Everhart rejects that even the largest tylosaurines preyed on full grown Elasmosaurus.

Well then I don't see why you think there was comparatively little prey available during that time; and that despite the preservation of that taxon being evidently problematic...

Again, Gigantophagy is not required. Predators could and can obviously get huge based on a generalist diet

I ask you evidences of a biodiversity in large and numerous potential preys comparable to the Miocene-Pliocene eras, don't turn the question to me, you're the first to suggest otherwise so bring material.

I've yet to see simethig suggested or claimed as comparable to the occurence of whales.

Predators can get big based on generalist diet but they can get big EASIER with vast sources of large preys.

You have given the answer why this is the case yourself, such trends are not being studied as extensively, neither are you inquiring about them.

but the presence of big pachycormid fish and giant pliosaurs in the same strata is already a correlation.

And you argue to have read Mchenry and argue with me ? I should do waste time to discuss with you actually :

Planktonivory, or giganto-carnivory analogous to that reconstructed for Carcharocles megalodon, are not considered likely for 10–20 tonne pliosaurs.


Really, don't discuss with me.

Perhaps if instead of telling me how worthless it is, you could actually properly read and consider my arguments and see whether they are valid.

They are not valid. You speculate with optimism, and since you cannot engage Kent or McHenry, you engage me like if I was the author of such claims.
You just wishe to see big things (as big as meg or Liv) during the Mesozoic. Once that was the pliosaurs, now that's the ichthysaurs, even though you have no material as back up.

"General patterns", yes, so don't hypothetise them into obligatory rules that have one single exception.

Are you tired? I have repeated this several times as general patterns, and that exceptions can/might occur.

For the rest, I don't care of your crying. You engage me, while I only report claims from Kent and McHenry, claims that either you're unable to understand by yourself as I've used several posts to clarify you their quotes, or either that you don't like (your tendency to want things biggers and bigger, like the average YT kid).

So if you have a problem with Kent and McHenry, go discuss with them, I won't do it for you.

[Life]

theropod

It is wise to settle for a middle-ground in a discussion in which you have little chance of getting your perceptions fully agreed to. If for some reason, you cannot reach a middle-ground, just state your opinion with (my reservations) kind of remark and let the debate cool down, before you begin anew. Also, input from scientists/experts is valuable in these discussions, regardless of our reluctance to accept them fully or not due to different reasons.

Grey

Several factors can contribute to gigantism in a life-form.

[Grey]

Sure, only, the gigantism in active macrophagous predators is favored by the occurrence of numerous and very large main preys. That's at least what suggests the observation of patterns.

This is no hazard that Livyatan and meg, the largest hypercarnivorous whale known, and megalodon, the largest predatory shark ever, occurred together at this specific time period. Both are substantially larger than any macrophagous (not theutivorous) marine reptiles described from Mesozoic environments.

This does not mean that some exception is impossible (they have yet to be known) but that's based on hard data so far.

I'm tired to discuss with members all the time speculating and never showing interest in the understanding of the authors I discuss with.

[Life]

I agree:-

"A correlation between the emergence of the giant shark Carcharocles megalodon and the Miocene diversification of the mysticetes has already been proposed. Considering the distinct increase in the range of sizes for mysticetes since the Langhian stage, progressively reaching greater maximum sizes (Fig. 4b and Supplementary Information), the record of two giant marine predators, C. megalodon and L. melvillei, in the same mysticete-rich Serravallian locality might be relevant." (Lambert et al., 2010)

Two factors are very important for evolution of gigantism among macropredators:-

1. Abundance in food supply
2. Favorable climatic conditions

Both of the aforementioned conditions should be met.

The conditions for evolution of gigantism among micropredators or herbivores are not so strict in contrast.