Megalodon vs. Livyatan melvillei

[theropod]

Oct 26, 2019 16:58:38 GMT 5 Life said:

3 decades is a lot of time to uncover traces of their dietary preferences.

There are no guarantees of finding a particular thing in the fossil record just because we feel like we should have found it by now.

Oct 26, 2019 16:58:38 GMT 5 Life said:

In the context of this thread, some members are jumping to conclusions in regards to what kind of prey Livyatan melvillei could 'realistically handle' and going as far as to infer that it could challenge an adult Megalodon in a confrontation - these assumptions are PREMATURE at this stage.

It would be premature at this stage to suggest that it could not.

Oct 26, 2019 16:58:38 GMT 5 Life said:

I am all for constructive/scholarly/scientific/meaningful discussions about animals under consideration in this thread, but this is an interspecific (versus) thread to begin with.

Yes, but my issue is that you are misconstruing "interspecific versus scenarios" into the primary driving force for biogeographical and macroevolutionary trends, which they simply are not, and using that as a justification to infer things relevant to this topic from those same trends (which aren’t even fully understood yet.

Now, the assumption that gigantic sharks spared stem physeteroids from 'predation' is erroneous (see Gilbert et al., 2018); Livyatan-types and gigantic sharks were aiming for access to same prey items, right? Trophic interactions were inevitable accordingly.

Firstly, nobody claimed sharks spared stem-physeteroids from predation, secondly predation and competition are not the same thing.

The most glaring/interesting observation is that Livyatan-types were unable to establish a 'cosmopolitan distribution' in the Miocene

Piazza et al. as well as myself have already pointed out potential reasons as well as caveats in that observation. I see no reason to reiterate them again, read my last post and/or Piazza et al. 2019.

You alluded to environmental considerations such as Livyatan-types being accustomed to colder climatic conditions but I find this reasoning problematic because of following observations; (1) glaciation of South Pole in PMMG is a continuous trend; (2) there are traces of Livyatan-types in the Northern hemisphere (e.g. WH023), and this particular fossil also provide evidence of a trophic interaction with a gigantic shark (you continue to dispel this notion but you clearly fail to understand that Megalodon only need to deliver a single bite to close the chapter of any stem physeteriod).

And that reasoning is in turn problematic because firstly, you do not seem to understand the difference between a trace fossil and proof of a trophic interaction between living animals, and because secondly, "Livyatan-types", meaning large raptorial stem-physeteroids, appear in the southern hemisphere alongside megalodon in the Lower and Middle Miocene, and coexisted with it right up until the lower Pliocene.

One of the best reconstructions indicating wider jaw dimensions than in great white shark (Grey ) as well as the sheer volume of flesh and bone it would cut through in view of biomechanical considerations for Megalodon. Now, keep in mind that this is merely jaw structure and not the whole chondrocranium which could provide us a true glimpse of how potent the biting prowess was.

This is still besides the point, it has nothing to do with whether or not Livyatan was cosmopolitan. And the chondocranium has no influence on the biting prowess whatsoever.

Teeth can offer a wealth of information about an animal, including clues about its age, when it lived, its diet and whether it had certain diseases. Megalodon’s teeth suggest its hunting style was likely a single-strike tactic, designed to immobilize its prey and allow it to bleed out, Perez said.

You are not telling me anything new here.

Temporal range of Livyatan melvillei seem to approach 11.6 Ma mark although Livyatan-types might have lasted longer as a whole but WE are not sure because the Pliocene record could be a case of a reworked sediment. Zygophyseter and Physeterula are reliably established in the Upper Miocene stratography.

Ah, reworked sediment? Who suggested that? I know this is possible, and is indeed the case with some of the younger records of megalodon teeth, but I have seen no suggestion whatsoever that the Pliocene cf. Livyatan teeth are allochthonous. We cannot just assume something is not from the formation is was found in because we don’t want it to. For all we know, the pliocene tooth record of Livyatan is just as solid as that of Megalodon.

The RED part is CORRECT because longest lasting stem physeteriods such as Acrophyseter and Physeterula vanished around 5.3 Ma mark; others vanished earlier.

Physeterula is not a stem-physeteroid, Acrophyseter does not appear to have been especially long-lasting (based on the very limited material that we have) and is not known to last up until that late, and the red part is not correct. Boessenecker must simply have been unaware of Pliocene Livyatan teeth, which were published about half a year after the paper you cite. So no wonder, really.

Emphasis mine. Gigantic sharks (Megalodon form) are the most likely factor in Livyatan-types not being able to achieve a cosmopolitan distribution and/or the primary driver of the extinction of stem physeteriods in the PMMG period but the resultant ecological void seems to have affected Megalodon in the largely unstable Pliocene subsequently. This inference is completely in line with findings of Gilbert et al (2018), privately sold WH023, and biomechanical considerations for Megalodon from Perez et al (2018).

Well coming from a biological and geological perspective, that is a plain a misinterpretation trying to explain every complexity of the fossil record and marine ecology by "who is the most awesome predatir", but I’ve already laid out all my reasons for saying that in this and the previous post.

I would not say that wolves can outcompete polar bears or hyenas can outcompete lions; does not sound realistic. Apex predators are such for a reason.

Some environments have more than one top-dog. Tigers may be outmatched by brown bears, but they are still apex predators. Orcas may not challenge bull Physeter, but they are still apex predators. Crocodiles and Lions are both apex predators in Africa today. As were multiple predators in earths history that coexisted.

Livyatan melvillei gives the vibe of being an interesting experiment of nature but it did not translate into an accomplished species.

It translated into the largest tetrapod jaw apparatus known to size, a raptorial predator the size of a sperm whale and with jaws 3 times the dimensions of an orca’s, that lasted for at least 6 million years alongside the largest shark that ever lived, achieved an at least circumpolar distribution in the southern hemisphere. I am not sure of your definition of an "accomplished species", but in my book, this certainly fits the bill.

Biologists are just as biased and/or shortsighted as people in other professions.

So people who fail to proclaim megalodon as clearly superior must be automatically biased? too bad.

Because isolated Physeteroid teeth are not necessarily diagnostic at the genus level, remember? I can play this game as well.

Ah, interesting. So when studies actually identify teeth as Livyatan (while differentiating them from other, non-diagnostic physeteroid teeth), you feel compelled to ignore them, but when a fossil sales websites posts a picture of something that reminds you of the shape of a Livyatan tooth that has a ghash-mark on it, you take that not only as irrefutable proof that this animal was indeed a Livyatan (without ever having examined the tooth, consulted with experts on physeteroid teeth, or having considered other options of taxonomic assignment), but was preyed on by megalodon? You were also more than happy to take into account isolated cf. Livyatan teeth to suggest these were from smaller individuals, even if there was no evidence for that. But once again, you are happy to ignore them now, when they actually do suggest something for real, namely a temporal range into the Pliocene?

At any rate, as I think I also wrote, at the very least the South African teeth are clearly raptorial stem-physeteroids, whether or not we trust their assignment to the genus Livyatan specifically. Therefore, as of the current data, your claim that megaldon outlived Livyatan is very suspect. Yet you are making that claim as if it were a fact.

Even in Cerro Colorado, a location in PERU, which is noted for its interesting environmental characteristics and/or excellent preservation of fossils, remains of Livyatan melvillei are visible only in the LOWER MIOCENE stratography.

The holotype of Livyatan is Tortonian, read Lambert et al. 2016. That is firstly Upper Miocene, and secondly means 11.6-7.2 Ma.

So you admit that your original claim about Livyatan-types being accustomed to colder climatic conditions was PREMATURE? Good.

I admit no such thing, as it was not a claim, it was a hypothesis, which I noted requires further data to substantiate. But at the very least it is a better hypothesis than yours, that megalodon waged some sort of war against Livyatan to prevent it from expanding into the northern hemisphere, if I’m getting you right.

Gigantic ones as well? I really doubt this.

I don’t see the relevance, but Bowhead whale?

Anti-trophical distribution of even beaked whales, is suspect. FYI: gisinecology.com/_files/PDFs%20of%20Case%20Studies/Global%20Distribution%20of%20Beaked%20Whales.pdf

Again, relevance? I suggest Davies 1963.

Davies, J.L. 1963. The Antitropical Factor in Cetacean Speciation. Evolution 17 (1): 107–116.

Distribution patterns of cetaceans are probably shaped by multiple factors but 'access to preferred prey' is very important consideration.

So you admit that you cannot simply break animal distributions down to whether there is another animal that could kill them in the environment in question? Good.

Stem physeteriods - all species considered - were operating in numerous environments back in Miocene much like killer whales today.

Yes, and stem-physeteroids apparently were cosmopolitan. That does not bode well for your hypothesis that megalodon "eradicated" other predators encraching on its territory, although once more, that Livyatan coexisted with megalodon in the souther hemisphere for millions of years made that hypothesis very unlikely to begin with. But this doesn’t necessarily mean every taxon of stem-physeteroid.

Livyatan melvillei, in particular, was risking potential confrontations with Megalodon for access to similar prey items on a frequent basis. In fact, to Megalodon, every cetacean was a FAIR GAME, particularly the bigger ones. This inference is in line with the observation of Gilbert et al (2018) as to why stem physeteriods did not had longevity in lifespans even though their assessment is restricted to Lee Creek population base. Competitive pressures from gigantic sharks would have an impact on distribution patterns of Livyatan melvillei - moreso than any other species in existence back then.

"more impact than other shark species" doesn’t equal "important impact"

How come great white sharks have their wide distribution according to your logic, despite the fact that they are fair game to orcas?

Oct 24, 2019 23:26:38 GMT 5 theropod said:

Because isolated Physeteroid teeth are not necessarily diagnostic at the genus level, and because. If we consider every large Physeteroid tooth to be from Livyatan, then there’s also a record of the taxon from the Netherlands (Reumer et al. 2017)…

OK, so what about this, do you count every large Physeteroid tooth as Livyatan now, and if so, how can you not conclude that it was present in the northern hemisphere?

Or should we maybe limit this to teeth identified as Livyatan in the published literature? In which case, Livyatan is so far restricted to the southern hemisphere, but just as long-lasting as megalodon, and probably not limited in its distribution due to competition with the shark, because it competed with the shark in the southern hemisphere as well.

I am aware of the fact that majority of stem physteriods fall into the 5-7 m TL range. Examples include Albicetus, Brygmophyseter, Zygophyseter and Physeterula.

Again, not a stem-physeteroid.

- WE should do the same for stem physeteriods.

Sample size considered in Gilbert et al (2018):

We measured the length and diameter of 276 complete physeteroid teeth from the Yorktown Formation of the Lee Creek Mine in collections at the USNM. Length was measured from the base of the tooth to the tip, and diameter was measured near the apex of the pulp cavity in all specimens. As indicated above, only teeth greater than 3.0 cm in length and/or greater than 1.0 cm in diameter were included in this study in order to minimize the likelihood of including teeth from multiple species. The condition of the cementum sheath was noted for each tooth. Analyses below relative to diameter consider only the 232 teeth with intact cementum.

These physeteroids were definitely not Livyatan, neither did the authors suggest anything along those lines, nor does the tooth morphology even remotely resemble it. Average adult size of some other physeteroid is about as relevant to that of Livyatan as average adult size of Cretalamna is to C. megalodon

Every type of stem physeteriod including Livyatan melvillei was accounted for in the aforementioned sample:

Is this Livyatan vs megalodon or "random average-sized stem-physeteroid vs megalodon"

INCLUSION of the gigantic forms such as Livyatan melvillei in the aforementioned sample, is the reason why the 'average adult size' of stem physeteriods titled towards the 10 m TL mark in the calculations of Gilber et al (2018) as shown in the following figure:

Err no, it is not.  This figure is not the "average adult size", it is the maximum adult size of specifically the Lee Creek Physeteroids, not all stem-physeteroids, and not Livyatan. Gilbert et al.’s estimates were made based on a regression of TL on tooth diameter, hence why they are not overly reliable.




Figure caption from Gilbert et al. 2018:

A, maximum adult body size calculated
from the relationship between maximum tooth diameter and maxi-
mum body length for males and females of 18 extant odontocete spe-
cies from Best (2007). The maximum observed dental diameter
(49 mm) and the mean measured tooth diameter plus 2 standard
deviations (38 mm) yield body lengths of 11.4 and 9.2 m, respectively
(bracketed by dark gray shading; pale gray–shaded envelope takes
into account the anticipated error based on within-tooth-row varia-
tion in tooth size).

SAM-PQHB-270 (Govendor, 2019)

SAM-PQHB-270 is a large, robust tooth root (222.14 mm) with the distal fragment of the crown preserved (Figure 10(a,b)) which is similar to cf. Zygophyseter sp. where the root length is 215 mm (NMR 9991–00010227) and 210 mm (NMR 9991–- 00010228) (Reumer et al. 2017), Acrophyseter (14–90.3 mm) but is smaller than Livyatan melvillei (maximum length >360 mm, Lambert et al. 2010). The root of SAM-PQHB-270 is more robust and wider than Zygophyseter varolai cf. Zygophyseter sp. and Acrophyseter deinodon. SAM-PQHB-270 is broad proximally and tapers to rounded point distally which differs from Livyatan melvillei which cylindrical along its length, but some do show a narrowing towards the distal end (Lambert et al. 2016; Figure 36O, p.56). Its widest diameter is 101.10 mm which is within the range of L. melvillei (81–111 mm) but is larger than Acrophyseter (18–32 mm), Zygophyseter (44.3–56 mm). The root has a slight curved compared with Zygophyseter varolai, cf. Zygophyseter sp. and Acrophyseter sp. where the root is distinctly curved proximally. The cementum is rough and uneven as compared with cf. Zygophyseter sp. where the cementum is smooth with some grooves and smooth in Zygophyseter varolai, Acrophyseter deinodon and Acrophyseter. The root is buccal-lingually flattened and the surface is flattened. There is no gingival collar as seen in Zygophyseter varolai, Acrophyseter deinodon. Just below the crown the root narrows. The broad distal end of the crown is preserved (about 31.1 mm long) and has a circular outline. The pulp cavity is closed suggesting an older individual possibly an adult (Hohn 2009; Lambert et al. 2016).

Observation: noticeably smaller than the largest teeth in Livyatan holotype.

Observation: noticeably smaller than the largest teeth in adult megalodon. ≠ Conclusion: Adult megalodon were smaller than we thought.

Anything else I am missing?

That all the isolated cf. Livyatan teeth, and those are the only ones that are relevant, are within the range of tooth diameters of the holotype. Therefore, all of them could be from holotype-sized individuals. Just like there being lots of small posterior megalodon teeth doesn’t make megalodon any smaller.

Therefore, 'average body size' of adult stem physeteriods [all manner of teeth considered] tilt towards 10 m TL mark (in line with assessment of Gilbert et al., 2018), although, as noted above, majority of stem physeteriods were smaller in reality (5-7 m TL range). Therefore, Livyatan-types are primarily responsible for the tilt towards 10 m TL mark.

Yes, so? Why is that important? there isn’t even such a thing as a "tilt towards the 10 m mark", average adult stem-physeteroids were likely well below that. The figure you are talking about doesn’t exist, and even if it did, would be irrelevant here.

What did I tell you earlier? Livyatan holotype is far above the 'average body size' consideration - extremely large stem physeteriod by any measure.

What is the problem with understanding the difference between "average adult stem-physeteroid" and "average adult Livyatan"? Do you also conflate "average adult orca" with "average adult delphinid"?

Voss et al (2019) reason that biting activities observed on skull structures indicate predation:

"Some Dorudon specimens bear bite marks made by B. isis [29, 30]. Although bite marks alone hardly allow one to distinguish between active predation and scavenging, most of the bite marks observed on dorudons are located on the head, more specifically, on the frontal. This indicates that the head was the preferred region for Basilosaurus attacks leading most efficiently to death [30]. Exactly the same situation is shown in Fig 2c in Collareta et al. [64] for the predatory giant megatooth shark Carcharocles megalodon that bit a diminutive baleen whale. If we assume Basilosaurus being a scavenger, we would expect that Basilosaurus preferencially fed on regions of the dorudon body other than the head, for example the tail or thoracic region. The latter is documented for another shark species, the Recent great white shark that, beyond preying on various pinnepeds, is also known to ordinarily scavenge on large whale carcasses [65]."

You should pay special attention to the bolded part, as that’s at the very core of the misunderstanding here.

Basilosaurus potentially attacking a juvenile of a smaller whale with a skull bite is an entirely different thing from megalodon attacking a similar-sized Livyatan, just like attacking a cetothere is.

Megalodon teeth are among the hardest of biological substances in existence, yet there are examples of these objects getting destroyed during the course of biting activities of Megalodon. These observations coupled with biomechanical considerations suggest that an adult Megalodon would be able to tear through the skull of Livyatan holotype as well.

Very unlikely from a biomechanical standpoint, but since neither of us is able to offer more than colorful speculations on this point, we should stop and agree that we do not know whether megalodon had the capability of biting through bone the size of the Livyatan skull.

The juvenile Megalodon (~6 m TL) was able to cut through the layers of skin, blubber and flesh all the way down to the bone which is very impressive in view of the sheer disparity in size of the macropredator and the whale involved in this particular case of trophic interaction. This whale died about 14 days later - succumbed to its wounds?

I already said it was impressive. I was merely correcting your erraneous statement that the shark "breached the whale’s chest cavity".

No modern-era shark is found to be that aggressive and capable,

Well, I know a video of a tiger shark eating a sick blue whale alive, and at least contributing to its death…

What if an adult Megalodon was responsible for the demise of Livyatan holotype? The latter died young, right?

Speculations like these lead down a rabbithole of wild imagination. What if an adult Livyatan was responsible for the demise of the Yorktown megalodon? See?

Remains of small sharks have been noticed in the stomach contents of extinct macropredators.

You cannot find stomach contents of an animal without first finding its postcranium. Until a Livyatan postcranium is found with signs of preserved stomach contents (which would be lucky enough as it is), we do not have any clue as to what they would contain or not contain. Even with just a limited number of individuals with preserved stomach contents, we could hardly be sure that was all it ever ate. I recall Tricas & McCosker’s study sampling several great white shark stomachs from different-sized individuals and not finding a single marine mammal, even though the latter are the primary food source of adult individuals.

Stomach contents of Livyatan melvillei are not necessary to determine what kind of prey stem physeteriods were targeting in general.

No, they are not, although they would be a great help. You were the one who came up with stomach contents.

While assessing trophic interactions of Megalodon, expect to see much more than bones of victims bearing dental imprints - all manner of damage actually. One cannot simply expect a Megalodon tooth to only inflict a cut on a bone while driven towards it with staggering forces, expect to see bony structures completely severed, bones cut into fragments and more. Heck, expect to see even broken Megalodon teeth under the weight of predatory pressures. So how can you tell the difference?

That is exactly my point. And similar injuries might be caused by a Livyatan attack, so we really may not be able to tell one from the other in some cases.

I am not even a paleontologist but I can understand how things are.

Well, luckily I am, and I think when I tell you that the fossil record is incomplete, you can trust that assessment. But if you do not, then go and read any introductory coursebook on palaeontology to understand I am right.

On the basis of discovery of large but isolated physeteriod teeth, gigantic stem physeteriods were 'suspected' to have existed long before discovery of the Livyatan holotype. For example, Jurassic Fight Club TV show (2008) portray B. shigensis to be in the size range of Livyatan-types and challenging Megalodon for supremacy about 2 years before the discovery of Livyatan holotype.

Yes, they portray Brygmophyseter shigensis as that big, erraneously. Just like the BBC portrayed Liopleurodon ferox as a 25 m monster. That was clearly not based on solid evidence. Hence why I wrote "show evidence", not speculations. Large teeth were known, but large teeth alone are not good evidence of size. See for example Albicetus, whose tooth diameters overlap those of the Livyatan holotype.

As pointed out above, Megalodon could disable/kill any whale with a single bite.

Yes, this is likely correct. Once more, not a thing anyone here seems to deny.

[sam1]

..just a notion in regards that "megalodon could kill any whale with a single bite".
Well, in some cases I can see that happening only via the bite on the root of the tail..which would not be risk-free at all if the target is big and powerful enough.
Imo, a blue whale and bowhead whale for example are very likely to survive a single bite from megalodon.
Bowhead whale has up to a 50cm thick layer of blubber on top of its vital musculature..so megalodon would just cut on the surface; the bowhead would roll and free itself with only  a nasty,  huge but superficial tear of the skin.
So megalodon would have to work a lot for that meal.
As for blue whale, it would also take the bite(fat layer protection on top of enormous body size) and then accelerate instantly, leaving the shark behind.

Sperm whale is another strong candidate for surviving a single bite

[theropod]

Such large whales were not around back then though, Livyatan is probably the largest Miocene cetacean. I do think that a single bite from a good-sized megalodon would be potentially fatal (or at least disabling) for pretty much anything swimming around back then, though not necessarily instantly.

[sam1]

Of course.. the statement I quoted seemed generalized so I adressed it.

[Infinity Blade]

Going a bit off on a tangent but I have a question: is bowhead whale blubber 50 cm thick everywhere? Or is that the maximum thickness localized at one body part? People often cite how thick say, skin or a layer of fat is, but at least skin isn't uniformly thick across the body. For example, elephant skin is up to 2.5-3 cm thick at one region, but considerably thinner at other parts.

[theropod]

Nope, blubber thickness in right whales varies depending on the position. www.int-res.com/articles/meps_oa/m438p267.pdf

[Life]

Oct 26, 2019 22:24:43 GMT 5 sam1 said:

..just a notion in regards that "megalodon could kill any whale with a single bite".
Well, in some cases I can see that happening only via the bite on the root of the tail..which would not be risk-free at all if the target is big and powerful enough.
Imo, a blue whale and bowhead whale for example are very likely to survive a single bite from megalodon.
Bowhead whale has up to a 50cm thick layer of blubber on top of its vital musculature..so megalodon would just cut on the surface; the bowhead would roll and free itself with only  a nasty,  huge but superficial tear of the skin.
So megalodon would have to work a lot for that meal.
As for blue whale, it would also take the bite(fat layer protection on top of enormous body size) and then accelerate instantly, leaving the shark behind.

Sperm whale is another strong candidate for surviving a single bite


View Attachment

You must be joking right?



SHARKZILLA was carefully designed to simulate the real thing but it is actually inferior to the real thing (i.e. sophistication of biology cannot be easily replicated mechanically and otherwise). Heck, Wroe et al. (2008) admitted that their 'software modeling' provide underestimates.

Some members here are in utter denial or have no idea about the raw power of gigantic sharks in question.

Have a good look at the sheer size of the jaw structure:



Those teeth are naturally designed to withstand extreme pressures of biting through bony structures and then some.

Even great white shark's jaw power will surprise you, if you have any idea. Don't be foolish.

[sam1]

This is exactly what I expected to see..Life's reply to my logical observation  with an image of jaw reconstruction and some lamentations of their unholy destructive force.. and there it came, SHARKZILLA.
You delivered and then some.

So by your "colorful imagination", I take it you assume a megalodon's 15cm teeth would just somehow snap through a 50cm of blubber AND all the meat AND bone beneath ..one second it's there, the next one there's just this gigantic hole spitting fountains of blood? You're basically saying a one bite from megalodon would finish off a blue whale, and a 100t whale with a freaking half meter thick "bite me" layer?
Is that correct?

A white shark? I wouldn't be surprised to know that many dolphins survived a full bite on a critical region from a much larger GWS.

[Life]

Oct 26, 2019 18:39:37 GMT 5 theropod said:

There are no guarantees of finding a particular thing in the fossil record just because we feel like we should have found it by now.

Thus far, nothing suggest that Livyatan melvillei was a big-game hunter in the league of Megalodon.

Oct 26, 2019 18:39:37 GMT 5 theropod said:

It would be premature at this stage to suggest that it could not.

Based on colorful imaginations?

Oct 26, 2019 18:39:37 GMT 5 theropod said:

Yes, but my issue is that you are misconstruing "interspecific versus scenarios" into the primary driving force for biogeographical and macroevolutionary trends, which they simply are not, and using that as a justification to infer things relevant to this topic from those same trends (which aren’t even fully understood yet.

Whatever WE can tell about extinct animals, is based on inferences drawn from fossil records only.

Oct 26, 2019 18:39:37 GMT 5 theropod said:

Firstly, nobody claimed sharks spared stem-physeteroids from predation, secondly predation and competition are not the same thing.

Some people assumed otherwise; I wanted to address this part therefore.

Oct 26, 2019 18:39:37 GMT 5 theropod said:

Piazza et al. as well as myself have already pointed out potential reasons as well as caveats in that observation. I see no reason to reiterate them again, read my last post and/or Piazza et al. 2019.

From Piazza et al. (2018):

"The reasons of the extinction of such predatory whales are still uncertain, but it is not improbable that it may be correlated with competition for food
resources with globicephaline delphinids. This hypothesis still rests on weak evidence and should be evaluated through findings of new specimens, as well as detailed analysis of the fossil record."

Nothing conclusive in that statement and even in their paper. Piazza et al. (2018) were/are not aware of WH023 (a Northern Hemisphere find). You have already admitted that your claim in regards to colder climatic conditions is "premature."

So?

Oct 26, 2019 18:39:37 GMT 5 theropod said:

And that reasoning is in turn problematic because firstly, you do not seem to understand the difference between a trace fossil and proof of a trophic interaction between living animals, and because secondly, "Livyatan-types", meaning large raptorial stem-physeteroids, appear in the southern hemisphere alongside megalodon in the Lower and Middle Miocene, and coexisted with it right up until the lower Pliocene.

I completely understand 'the difference between a trace fossil and proof of a trophic interaction' (bitten bones versus bones showing signs of healing after a violent event); I have read lot of papers, and I am in the profession of academics.

In the context of bitten bones, WE cannot tell with 100% certainty (scavenging or predation). This is why authors often take a leap of faith and assume predation events on the basis of 'additional set of observations' and/or logical inferences.

Yes, Livyatan-types co-existed with gigantic sharks for like 6 million years? Very impressive.

Oct 26, 2019 18:39:37 GMT 5 theropod said:

This is still besides the point, it has nothing to do with whether or not Livyatan was cosmopolitan. And the chondocranium has no influence on the biting prowess whatsoever.

I think you missed the point in its entirety. Recheck my earlier post and try to figure out the context behind that jaw reconstruction - why I posted it.

Chondocranium can provide a meaningful idea about musculature of jaw structure (size and mass of muscles).

Oct 26, 2019 18:39:37 GMT 5 theropod said:

You are not telling me anything new here.

Perhaps this point have something to do with the jaw reconstruction?

Oct 26, 2019 18:39:37 GMT 5 theropod said:

Ah, reworked sediment? Who suggested that? I know this is possible, and is indeed the case with some of the younger records of megalodon teeth, but I have seen no suggestion whatsoever that the Pliocene cf. Livyatan teeth are allochthonous. We cannot just assume something is not from the formation is was found in because we don’t want it to. For all we know, the pliocene tooth record of Livyatan is just as solid as that of Megalodon.

REVISITED CLADE of sperm whales from Lambert et al. (2016):



Records of Livyatan-types compiled by Piazza et al (2018):



1. Livyatan-types approach 8.7 Ma mark.
2. No known stem physeteriod approached/crossed 5.3 Ma boundary.

Early Pliocene Livyatan cf. reported in Govender (2019) approach 5 Ma mark somehow which is unusual but this example should be revisited in the context of dating; Hondeklip Bay is a region of climatic upheavals as well as a former mining zone. This was a warm water environment in Pliocene by the way (contradicting the claims of Livyatan-types being accustomed to colder climatic conditions).

The analysis of fossil cetaceans from Hondeklip Bay has identified the following mysticetes: Balaenopteridae indet. (sp.1), cf. Eschrichtius sp., Balaenopteridae indet., cf. Plesiobalaenoptera as well as a balaenid, Balaenidae indet. Odontocetes identified include Physeteroidea indet., and cf. Livyatan along with an unidentified neonate delphinid. Hondeklip Bay shares the balaenopterid cf. Plesiobalaenoptera and the phocid seal, Homiphoca, with Langebaanweg while it does not share any taxa with Koeberg [indet. balaenopterids, “B.” borealina, Diunatans sp. 1, Fragilicetus sp., porpoise (cf. Autralithax), beaked whale (cf. Izikoziphius)] (Govender et al. 2016; Govender 2018; Govender 2019). Both localities are more than 400 km south in the southwestern Cape. Taken together these three sites suggest a diverse cetacean fauna along the South African west coast 5Ma similar to the extant population (Cummings 1985; Winn and Reichley 1985; Best 2007).

Even if taken at face value, this might be a small isolated population base of Livyatan-types because stem physeteriods are no longer globally visible beyond 5.3 Ma boundary.

Oct 26, 2019 18:39:37 GMT 5 theropod said:

Physeterula is not a stem-physeteroid, Acrophyseter does not appear to have been especially long-lasting (based on the very limited material that we have) and is not known to last up until that late, and the red part is not correct. Boessenecker must simply have been unaware of Pliocene Livyatan teeth, which were published about half a year after the paper you cite. So no wonder, really.

See above.

Oct 26, 2019 18:39:37 GMT 5 theropod said:

Well coming from a biological and geological perspective, that is a plain a misinterpretation trying to explain every complexity of the fossil record and marine ecology by "who is the most awesome predatir", but I’ve already laid out all my reasons for saying that in this and the previous post.

My assessment is not invalidated (see above); Boessenecker et al (2018) have also alluded to the same:

Many extant genera of cetaceans first appeared during the Pliocene (Fordyce & Muizon, 2001), apparently temporally coincident with the extinction of Otodus megalodon, but with uncertain relevance. Other biotic effects have been hypothesized to have affected or been driven by Otodus megalodon. Recently described macrophagous sperm whales appear to have been diverse worldwide in the middle and late Miocene, were similar in size to Otodus megalodon, and were likely competing apex predators (Lambert et al., 2010). A high diversity of small-bodied baleen whales during the middle Miocene is implicated in supporting such an assemblage of gigantic predators (Lambert et al., 2010; Collareta et al., 2017). Similarly, Lindberg & Pyenson (2006) noted that the extinction of Otodus megalodon is roughly contemporaneous with the earliest fossil occurrences of killer whales (Orcinus) in the fossil record, and perhaps competition with killer whales during the Pliocene could have acted as a driver in the extinction of Otodus megalodon. However, the Neogene fossil record of Orcinus is limited to two occurrences: an isolated tooth from Japan (Kohno & Tomida, 1993), and the well-preserved skull and skeleton of Orcinus citoniensis from the late Pliocene of Italy (Capellini, 1883). Furthermore, Orcinus citoniensis was small in comparison to extant Orcinus orca (est. four m body length: Heyning & Dahlheim, 1988) and possessed a higher number of relatively smaller teeth and narrower rostrum (Bianucci, 1996), and was probably not an analogous macrophagous predator. Because fossils of Orcinus are not widespread during the Pliocene, claims of competition between Otodus megalodon and Orcinus are problematic. Furthermore, the decline and loss of cosmopolitan macrophagous physeteroids (Tortonian-Messinian; Lambert et al., 2010) appears to have predated the early Pliocene extinction of Otodus megalodon by several million years.

No shift in the bigger picture.

Oct 26, 2019 18:39:37 GMT 5 theropod said:

Some environments have more than one top-dog. Tigers may be outmatched by brown bears, but they are still apex predators. Orcas may not challenge bull Physeter, but they are still apex predators. Crocodiles and Lions are both apex predators in Africa today. As were multiple predators in earths history that coexisted.

Sure.

Oct 26, 2019 18:39:37 GMT 5 theropod said:

It translated into the largest tetrapod jaw apparatus known to size, a raptorial predator the size of a sperm whale and with jaws 3 times the dimensions of an orca’s, that lasted for at least 6 million years alongside the largest shark that ever lived, achieved an at least circumpolar distribution in the southern hemisphere. I am not sure of your definition of an "accomplished species", but in my book, this certainly fits the bill.

Forgive me father for I have sinned...

Oct 26, 2019 18:39:37 GMT 5 theropod said:

So people who fail to proclaim megalodon as clearly superior must be automatically biased? too bad.

Those who excercize selective judgement. Too bad indeed.

Oct 26, 2019 18:39:37 GMT 5 theropod said:

Ah, interesting. So when studies actually identify teeth as Livyatan (while differentiating them from other, non-diagnostic physeteroid teeth), you feel compelled to ignore them, but when a fossil sales websites posts a picture of something that reminds you of the shape of a Livyatan tooth that has a ghash-mark on it, you take that not only as irrefutable proof that this animal was indeed a Livyatan (without ever having examined the tooth, consulted with experts on physeteroid teeth, or having considered other options of taxonomic assignment), but was preyed on by megalodon? You were also more than happy to take into account isolated cf. Livyatan teeth to suggest these were from smaller individuals, even if there was no evidence for that. But once again, you are happy to ignore them now, when they actually do suggest something for real, namely a temporal range into the Pliocene?

See above.

Oct 26, 2019 18:39:37 GMT 5 theropod said:

At any rate, as I think I also wrote, at the very least the South African teeth are clearly raptorial stem-physeteroids, whether or not we trust their assignment to the genus Livyatan specifically. Therefore, as of the current data, your claim that megaldon outlived Livyatan is very suspect. Yet you are making that claim as if it were a fact.

See above.

Yes, Megalodon absolutely outlived all stem physeteriods in prehistory, and the most likely candidate for driving THEM to extinction (assuming biotic factors).

Not those SUPER DUPER MARTIAN KAIJU DELPHINIDS once again.

Oct 26, 2019 18:39:37 GMT 5 theropod said:

The holotype of Livyatan is Tortonian, read Lambert et al. 2016. That is firstly Upper Miocene, and secondly means 11.6-7.2 Ma.

See above.

Oct 26, 2019 18:39:37 GMT 5 theropod said:

I admit no such thing, as it was not a claim, it was a hypothesis, which I noted requires further data to substantiate. But at the very least it is a better hypothesis than yours, that megalodon waged some sort of war against Livyatan to prevent it from expanding into the northern hemisphere, if I’m getting you right.

You need to revisit your hypothesis actually. Hondeklip Bay was a warm water environment back in Early Pliocene around 5 Ma mark by the way.

It is not unrealistic to assume that gigantic sharks and stem physeteriods were clashing for supremacy around the world because both CAMPS desired access to same prey items. Since gigantic sharks eventually prevailed in this BIOTIC WARFARE DYNAMIC, this observation is clearly UNSETTLING to those who have been touting supremacy of marine mammals over sharks on the grounds of seemingly one-sided outcomes of trophic interactions involving killer whales and great white sharks in modern times. These utterly biased individuals completely failed to understand any form of difference between extinct gigantic sharks (Megatoothed lineage) and modern white sharks (Smalltoothed lineage), and the list includes marine biologists as well. Really sad.

Oct 26, 2019 18:39:37 GMT 5 theropod said:

I don’t see the relevance, but Bowhead whale?

How is a modern-era baleen whale analogous to ancient stem physeteriods?

North Pole is plankton-rich environment so virtually all known baleen whales are expected to lurk there and/or adapt to those conditions. These are highly specialized marine mammals to begin with. However, baleen whales can inhabit relatively warmer environments.

Oct 26, 2019 18:39:37 GMT 5 theropod said:

Again, relevance? I suggest Davies 1963.

Davies, J.L. 1963. The Antitropical Factor in Cetacean Speciation. Evolution 17 (1): 107–116.

livyatan-types would want to expand worldwide (WH023 is a solid reminder).

However, different species of stem physeteriods (territorial tendencies?) as well as population bases (concentrations) of gigantic sharks would complicate the matter....

Oct 26, 2019 18:39:37 GMT 5 theropod said:

So you admit that you cannot simply break animal distributions down to whether there is another animal that could kill them in the environment in question? Good.

Ever heard of 'competitive exclusion'?

Relevant studies:-

1) Papastamatiou, Y. P., Wetherbee, B. M., Lowe, C. G., & Crow, G. L. (2006). Distribution and diet of four species of carcharhinid shark in the Hawaiian Islands: evidence for resource partitioning and competitive exclusion. Marine Ecology Progress Series, 320, 239-251.

2) Brunnschweiler, J. M., Abrantes, K. G., & Barnett, A. (2014). Long-term changes in species composition and relative abundances of sharks at a provisioning site. PLoS One, 9(1), e86682.

3) Heithaus, M. R. (2001). Predator–prey and competitive interactions between sharks (order Selachii) and dolphins (suborder Odontoceti): a review. Journal of Zoology, 253(1), 53-68.

Purdy et al (1996) attempted to map 'competitive exclusion' behavior of Megalodon and they noted that megatoothed sharks subjected smalltoothed sharks to 'competitive exclusion' around the world; traces of overlaps were deemed as sensitive to timing factor. Diedrich (2013) also complemented observations of Purdy et al (1996) in his work. This is why I find the notion of competition between great white sharks and Megalodon problematic because why would great white sharks risk potential confrontations with relatively larger and more formidable counterparts?

Environmental pressures such as glaciation in South Pole (Miocene) followed by glaciation in North Pole (Pliocene) as well as a series of geographical developments in Pliocene including The Messinian Salinity Crisis as well as eventual closure of the Isthmus of Panama, facilitated collapse of distinct population bases (concentrations) of Megalodon one-by-one, and survivors found themselves cut-off from numerous food-rich environments consequently. Under these circumstances, prior disappearance of stem phyeteriods from around the world proved FATAL...

Oct 26, 2019 18:39:37 GMT 5 theropod said:

Yes, and stem-physeteroids apparently were cosmopolitan. That does not bode well for your hypothesis that megalodon "eradicated" other predators encraching on its territory, although once more, that Livyatan coexisted with megalodon in the souther hemisphere for millions of years made that hypothesis very unlikely to begin with. But this doesn’t necessarily mean every taxon of stem-physeteroid.

See above.

Yes, Livyatan-types seemingly held their ground in the Southern hemisphere for millions of years (this might be due to abundance of energy-rich food sources in the Southern hemisphere) but they were unable to expand in the Northern hemisphere because BIOTIC pressures were possibly far greater in the Northern hemisphere.

Information about distribution patterns of stem physeteriods (all species) is scarce. However, distribution pattern of gigantic sharks have been mapped to a reasonable extent through the ages:



1. Gigantic sharks had a significant presence in the Northern hemisphere (continuous trend) but also encroached into regions inhabited by the Livyatan-types in the Southern hemisphere [most prominent in Late Miocene].

2. The isolated Livyatan cf. fossil reported from the Hondeklip Bay is in a region where Megalodon is absent at this point in time but smalltoothed sharks are present (Govender, 2019).

Oct 26, 2019 18:39:37 GMT 5 theropod said:

"more impact than other shark species" doesn’t equal "important impact"

How come great white sharks have their wide distribution according to your logic, despite the fact that they are fair game to orcas?

See below.

Refer to this study: Heithaus, M. R. (2001). Predator–prey and competitive interactions between sharks (order Selachii) and dolphins (suborder Odontoceti): a review. Journal of Zoology, 253(1), 53-68.

Oct 24, 2019 23:26:38 GMT 5 theropod said:

Or should we maybe limit this to teeth identified as Livyatan in the published literature? In which case, Livyatan is so far restricted to the southern hemisphere, but just as long-lasting as megalodon, and probably not limited in its distribution due to competition with the shark, because it competed with the shark in the southern hemisphere as well.

Ignoring privately-owned fossil records is not helpful, in a forum-based discourse to say the least.

Oct 24, 2019 23:26:38 GMT 5 theropod said:

Again, not a stem-physeteroid.

Last one? Fair.

Oct 24, 2019 23:26:38 GMT 5 theropod said:

Is this Livyatan vs megalodon or "random average-sized stem-physeteroid vs megalodon"

How about you drop your focus on the 'average adult size' for gigantic sharks in view of the Carharocles chubutensis-to-Megalodon transitions in Miocene (see Perez et al., 2019)? Pimiento et al (2014) and Pimiento and Balk (2015) do not take these transitions into consideration. It was the Megalodon form that was pushing boundaries in terms of size; largest teeth belong to Megalodon form only.



Otherwise, you need to consider MEAN of Gilbert et al (2018) for potential comparisons with Megalodon because this MEAN was obtained from extensive number of sperm whale teeth.

Oct 24, 2019 23:26:38 GMT 5 theropod said:

That all the isolated cf. Livyatan teeth, and those are the only ones that are relevant, are within the range of tooth diameters of the holotype. Therefore, all of them could be from holotype-sized individuals. Just like there being lots of small posterior megalodon teeth doesn’t make megalodon any smaller.

Not really.

SAM-PQHB-270 diameter = 101.10 mm
SAM-PQHB-265 = 104.46 mm
MML 882 = 74 mm
BAR-2601 = 72 mm
NMR 10227 = 62 mm
NMR 10228 = 85 mm

Diameter of the teeth in Livyatan holotype fall in the 81–111 mm range. However, these teeth are much larger than the isolated teeth on average, particularly in the TH aspect.

Oct 24, 2019 23:26:38 GMT 5 theropod said:

Yes, so? Why is that important? there isn’t even such a thing as a "tilt towards the 10 m mark", average adult stem-physeteroids were likely well below that. The figure you are talking about doesn’t exist, and even if it did, would be irrelevant here.

See above.

Oct 24, 2019 23:26:38 GMT 5 theropod said:

What is the problem with understanding the difference between "average adult stem-physeteroid" and "average adult Livyatan"? Do you also conflate "average adult orca" with "average adult delphinid"?

See above.

Oct 24, 2019 23:26:38 GMT 5 theropod said:

Basilosaurus potentially attacking a juvenile of a smaller whale with a skull bite is an entirely different thing from megalodon attacking a similar-sized Livyatan, just like attacking a cetothere is.

What can you tell about the size of the owner of WH023 as well as the Megalodon that is responsible for damaging/dislodging it?

Oct 24, 2019 23:26:38 GMT 5 theropod said:

Very unlikely from a biomechanical standpoint, but since neither of us is able to offer more than colorful speculations on this point, we should stop and agree that we do not know whether megalodon had the capability of biting through bone the size of the Livyatan skull.

Your disbelief in this regard is not scientifically established.

If I highlight the observation of even large whales being literally chomped in half or missing huge chunks of body parts, you will counter with the usual SCAVENGING line-of-thought.



SHARKZILLA is carefully constructed to simulate Megalodon's jaw power but even this mechanical behemoth falls short in comparison to the real thing (sophistication of biological apparatus is not easy to replicate mechanically and otherwise). However, even this crude vessel have no issue crushing massive pieces of metal and wood. I have seen a video in which this crude vessel crushed a stainless steel Mountain Bike as if it was a chewing gum.

You are undeniably very talented and informative but you disappoint me sometimes. Now I understand why there is a massive shortage of enlightening publications about ancient behemoths Megalodon and even Livyatan melvillei.

In one of the National documentaries, I literally heard one paleontologist saying this about Megalodon: "WE do not know what foods they were eating..." GODZILLA FACEPALM

H1: Megalodon was eating plankton
H2: Megalodon was eating sea-snakes
H3: Megalodon was eating humans

Oct 24, 2019 23:26:38 GMT 5 theropod said:

I already said it was impressive. I was merely correcting your erraneous statement that the shark "breached the whale’s chest cavity".

Right.

Now imagine what an adult Megalodon could do to the same whale.

Oct 24, 2019 23:26:38 GMT 5 theropod said:

Well, I know a video of a tiger shark eating a sick blue whale alive, and at least contributing to its death…

I have seen this video; that blue whale could barely move. Therefore, this analogy falls short in comparison to the case study in focus (i.e. juvenile Megalodon versus a much larger healthy whale).

Although I would like to point out that Tiger sharks and Bull sharks are very curious animals and can be really aggressive at times. But none hold a candle to Megalodon.

Oct 24, 2019 23:26:38 GMT 5 theropod said:

Speculations like these lead down a rabbithole of wild imagination. What if an adult Livyatan was responsible for the demise of the Yorktown megalodon? See?

No sign of the Livyatan-types in the Yorktown formation (Govender, 2019).

By the way, how is my claim unrealistic? What happened to the remainder of the holotype? Ah yes, WH023 represent SCAVENGING, right? Hmm.

Oct 24, 2019 23:26:38 GMT 5 theropod said:

You cannot find stomach contents of an animal without first finding its postcranium. Until a Livyatan postcranium is found with signs of preserved stomach contents (which would be lucky enough as it is), we do not have any clue as to what they would contain or not contain. Even with just a limited number of individuals with preserved stomach contents, we could hardly be sure that was all it ever ate. I recall Tricas & McCosker’s study sampling several great white shark stomachs from different-sized individuals and not finding a single marine mammal, even though the latter are the primary food source of adult individuals.

Fair enough.

Oct 24, 2019 23:26:38 GMT 5 theropod said:

No, they are not, although they would be a great help. You were the one who came up with stomach contents.

I am just surprised that 3 decades of studying stem physeteriods have not yielded much in the context of dietary preferences of these animals.

Oct 24, 2019 23:26:38 GMT 5 theropod said:

That is exactly my point. And similar injuries might be caused by a Livyatan attack, so we really may not be able to tell one from the other in some cases.

I am not so sure. Livyatan's jaw structure look formidable but its teeth are not efficient cutting tools. This macropredator gives the impression of being a cruncher, trapping and/or crushing bony fishes and/or marine mammals of certain size within its jaw.



Teeth in the upper jaw are pointed in the right direction but teeth in the lower jaw look like intended to prevent escape of a trapped prey item?

But of-course, dry skull experiments are necessary to gain meaningful insight.

Oct 24, 2019 23:26:38 GMT 5 theropod said:

Well, luckily I am, and I think when I tell you that the fossil record is incomplete, you can trust that assessment. But if you do not, then go and read any introductory coursebook on palaeontology to understand I am right.

I see.

Oct 24, 2019 23:26:38 GMT 5 theropod said:

Yes, they portray Brygmophyseter shigensis as that big, erraneously. Just like the BBC portrayed Liopleurodon ferox as a 25 m monster. That was clearly not based on solid evidence. Hence why I wrote "show evidence", not speculations. Large teeth were known, but large teeth alone are not good evidence of size. See for example Albicetus, whose tooth diameters overlap those of the Livyatan holotype.

I understand but what about TH aspect?

Oct 24, 2019 23:26:38 GMT 5 theropod said:

Yes, this is likely correct. Once more, not a thing anyone here seems to deny.

Actually I see denials in this very page.

[Life]

Oct 27, 2019 3:20:29 GMT 5 sam1 said:

This is exactly what I expected to see..Life's reply to my logical observation  with an image of jaw reconstruction and some lamentations of their unholy destructive force.. and there it came, SHARKZILLA.
You delivered and then some.

So by your "colorful imagination", I take it you assume a megalodon's 15cm teeth would just somehow snap through a 50cm of blubber AND all the meat AND bone beneath ..one second it's there, the next one there's just this gigantic hole spitting fountains of blood? You're basically saying a one bite from megalodon would finish off a blue whale, and a 100t whale with a freaking half meter thick "bite me" layer?
Is that correct?

A white shark? I wouldn't be surprised to know that many dolphins survived a full bite on a critical region from a much larger GWS.

Jaw dimensions make absolute difference even with a capable dentition. Megalodon had massive jaw dimensions (A3 is not small and inverted like in the Great white shark). Upcoming study involving member Grey will cover this reality.

"Within an hour, we’re off-roading in a landscape formed over millions of years by colliding tectonic plates. Our first stop: a large fossilized whale skeleton that includes eye sockets, a skull, and a partial spine and vertebrae. So what happened to the rest? “Erosion wouldn’t destroy half a whale,” Roberto says. “No, the lower part had to be taken by something strong, and that’s the megalodon. See the sharp break in the spine? Sometimes you’ll even find teeth marks on the bones.” All around us are earthy-looking heaps, more fossilized skeletons, but Roberto is barely interested in the whales all he can think about are megalodons."

Imagine the jaw dimensions of that behemoth.

SHARKZILLA experiment indicate that Megalodon would have no trouble biting through thick layers of blubber and flesh. I expect you not to be visual-impaired or are you?

Ever seen the damage a great white shark (6m TL) can inflict? A great white of this size can literally bite a large dolphin into half. Don't be naive.

100 foot blue whale is an outlier in terms of size (not common occurrence). A whale of this size might take a few bites to go down. However, adult Livyatan or adult Humpback whale? Single bite from an adult Megalodon is enough.

[theropod]

sam1

source
(Tiger shark, but same principle)


source


source


Shark bites can and do go very deep. Far deeper than just the length of their teeth. Soft tissue compresses under the load of the bite and the jaws go in like a sawblade. A single bite can indeed be devastating. Especially on smaller prey.


But of course shark bites also can and do fail to cause such injuries frequently, especially in larger animals (larger girth=larger gape=less force and less tissue caught between opposing jaws), otherwise scars like these would not exist.

source

Shark bites have awesome destructive power. I could even envision a large megalodon causing debilitating and potentially fatal injuries to even a bowhead or blue whale with one or two bites. At least I certainly won’t call someone delusional for thinking so. Neither would I call someone doubting this delusional.
It is also possible that it would (frequently) fail to do so, due to a combination the high girth and the thick blubber layer. Depends also on the circumstances and how much the whale struggles, living targets aren’t static blobs just holding still to be bitten.
More biomechanical testing would of course be needed to ascertain the plausibility of such a fatal bite, although designing an appropriate experiment would obviously be very challenging. In any case, it is most likely that against large whales, the shark would try to target the part where a first bite would have maximum effect, severing the swimming muscles and large blood vessels in the tail, and come back for more bites if necessary. That does not mean it could bite any body part of any size of whale it wanted and expect to kill it.

Also, we should not conflate the ability to saw through bones with the ability to saw through any size of bone, ever. In fossil megalodon bite marks, we can clearly observe the deepest the teeth can go into bone. Any bone larger than that would not be bitten through. Megalodon is still a shark, not some mythical monster without biological limitations. Shark teeth are loosely implanted in the dermis. If the load on a shark tooth becomes too large (such as being caught on an overly large piece of bone) it falls out. Period.
And they have limitations. I don’t appreciate being called delusional for acknowledging those limits.

If nobody who does not subscribe to the belief that this shark could easily kill anything in existence, ever, instantly, with a single bite and saw through the biggest bone is in their right mind, then there is truly no reason to continue this discussion at this point.

[Life]

Oct 27, 2019 3:59:23 GMT 5 theropod said:

sam1

source
(Tiger shark, but same principle)


source


source


Shark bites can and do go very deep. Far deeper than just the length of their teeth. Soft tissue compresses under the load of the bite and the jaws go in like a sawblade. A single bite can indeed be devastating. Especially on smaller prey.


But of course shark bites also can and do fail to cause such injuries frequently, especially in larger animals (larger girth=larger gape=less force and less tissue caught between opposing jaws), otherwise scars like these would not exist.

source

Shark bites have awesome destructive power. I could even envision a large megalodon causing debilitating and potentially fatal injuries to even a bowhead or blue whale with one or two bites. At least I certainly won’t call someone delusional for thinking so. Neither would I call someone doubting this delusional.
It is also possible that it would (frequently) fail to do so, due to a combination the high girth and the thick blubber layer. Depends also on the circumstances and how much the whale struggles, living targets aren’t static blobs just holding still to be bitten.
More biomechanical testing would of course be needed to ascertain the plausibility of such a fatal bite, although designing an appropriate experiment would obviously be very challenging. In any case, it is most likely that against large whales, the shark would try to target the part where a first bite would have maximum effect, severing the swimming muscles and large blood vessels in the tail, and come back for more bites if necessary. That does not mean it could bite any body part of any size of whale it wanted and expect to kill it.

Also, we should not conflate the ability to saw through bones with the ability to saw through any size of bone, ever. In fossil megalodon bite marks, we can clearly observe the deepest the teeth can go into bone. Any bone larger than that would not be bitten through. Megalodon is still a shark, not some mythical monster without biological limitations. Shark teeth are loosely implanted in the dermis. If the load on a shark tooth becomes too large (such as being caught on an overly large piece of bone) it falls out. Period.
And they have limitations. I don’t appreciate being called delusional for acknowledging those limits.

If nobody who does not subscribe to the belief that this shark could easily kill anything in existence, ever, instantly, with a single bite and saw through the biggest bone is in their right mind, then there is truly no reason to continue this discussion at this point.

Again, SIZE of the shark involved - is the key. How big was the shark which attacked each of these animals? These minute details are really helpful.

My arguments are in line with the assertion of marine biologist Victor J. Perez in regards to inferred destructive prowess of Megalodon. He have lot of exposure to these fossils, and examples of trophic interactions involving Megalodon in which prey items escaped death are exceedingly rare (only 2 examples). Among these two, a juvenile Megalodon was involved in attacking a much larger whale. In the 2nd case, a fractured bone of a whale have been found which is indicative of application of brute force from a Megalodon of unknown size but the whale somehow survived.

Bite marks are not necessarily indicative of jaw power in the case of sharks.

However, take a look at following example:



A seemingly robust fossil whale bone found cleaved into half by a Megalodon tooth. Now that is indicative of tremendous jaw power.

Similarly, Megalodon teeth found to be missing chunks even though these are easily among the hardest of organic substances ever.



Cannot get any better than that.

Yes, Megalodon teeth could detach during the course of an attack on a large cetacean. An example below.



That is why being able to replace broken and/or missing teeth, is an excellent biological capability.

Relevant experts have already cautioned that even though modern lifeforms can be excellent teachers, ground realities of ancient times are not necessarily represented in this age. Megalodon have no true analogue in modern times. Similarly, Livyatan melvillei have no true analogue in modern times. Therefore, our knowledge of both is limited.

I do not think anybody have disrespected you in person in this discussion, wasn't my intention to say the least. However, I felt the need to bring some observations to the attention of all, and rightfully so.

[dinosauria101]

Life

So what you are saying from your 1st big post today is that Megalodon was probably a much, MUCH bigger animal than even the biggest Leviathans?
I'll respond to more later, when I have time

[theropod]

It would be premature at this stage to suggest that it could not.

Based on colorful imaginations?

Based on evidence.

Whatever WE can tell about extinct animals, is based on inferences drawn from fossil records only.

Yes. So we should stick to the inferences we can actually draw from the fossils, and not those we’d only like to imagine we can draw.

Some people assumed otherwise; I wanted to address this part therefore.

Where did anyone claim that? I am perfectly familiar with Gilbert et al. 2018 and the likelihood that smaller stem-physeteroids were subject to predation pressure by both megalodon, and potentially other stem-physeteroids. I also still fail to see what’s so remarkable about this, as both megalodon and Livyatan are probably 10 times the size of those animals, so it’s to be expected they would have a higher trophic position.

Nothing conclusive in that statement and even in their paper. Piazza et al. (2018) were/are not aware of WH023 (a Northern Hemisphere find). You have already admitted that your claim in regards to colder climatic conditions is "premature."

A single tooth, not properly described or studied, privately sold, bearing a purported bite mark is not solid evidence for ecological relationships on a global scale and across millions of years, yet you seem to be basing the largest part of your argument on the specimen in question, even going so far as to suggest C. megalodon preyed on Livyatan.

I completely understand 'the difference between a trace fossil and proof of a trophic interaction' (bitten bones versus bones showing signs of healing after a violent event); I have read lot of papers, and I am in the profession of academics.

Well then you must see that the tooth you keep going on and on about is not proof of a trophic interaction. Being a tooth, obviously it cannot show signs of remodeling.

Yes, Livyatan-types co-existed with gigantic sharks for like 2.2 million years. Very impressive.

Age of oldest described cf. Livyatan teeth (Piazza et al. 2018): Saladar Member, Gran Bajo del Gualicho Formation, Early-Middle Miocene, ≥11.6 ma

Age of Livyatan melvillei holotype (Lambert et al. 2016) : Base of Pisco Formation, Tortonian, 9.9-8.9 Ma

Age of youngest described cf. Livyatan teeth (Govender et al. 2019): Avontuur member, Hondeklip Bay formation, Zanclean, ~5 Ma

= temporal range of at least 6.6 Ma ≠ 2.2 Ma

In the context of bitten bones, WE cannot tell with 100% certainty (scavenging or predation). This is why authors often take a leap of faith and assume predation events on the basis of 'additional set of observations' and/or logical inferences.

Science ≠ "Faith"

That’s precisely why good scientists do not take "leaps of faith", but rather base their conclusions on evidence, if available, or don’t make conclusions, if there isn’t any.

In the case of the bitten tooth, there isn’t any. Although it is certainly more parsimonious in this case to assume scavenging.

Chondocranium can provide a meaningful idea about musculature of jaw structure (size and mass of muscles).

Jaw muscles tend to attach to the jaws. Pretty much all the chondocranium would do is satisfy the need to make the shark head look bigger, without any relevance to the jaws themselves.

REVISITED CLADE of sperm whales from Lambert et al. (2016):

Records of Livyatan-types compiled by Piazza et al (2018):

1. Livyatan-types approach 8.7 Ma mark.
2. No known stem physeteriod approached/crossed 5.3 Ma boundary.

If not to actively mislead people, then why do you keep posting outdated ocurrence data as if it had some relevance?

Even if taken at face value, this might be a small isolated population base of Livyatan-types because stem physeteriods are no longer globally visible beyond 5.3 Ma boundary.

There are Pliocene teeth from Australia (still undescribed, but referred to Livyatan in the recent SVP abstract) and Miocene or Pliocene teeth from the Bahia Inglesa Formation (same abstract). That would be more like half the ocurrences we have of Livyatan so far then. How do you decide which half is the outlier? Based on what suites your hypothesis that megalodon is the reason for the decline of stem-physeteroids? In good science, the hypothesis must be shaped by the evidence, not the other way around.
Perhaps we could stop grasping at straws to come up with a way to explain away this evidence, and simply accept that these are Pliocene Livyatan (or at least large stem-physeteroid) teeth based on the best currently available data?

Physeterula is not a stem-physeteroid, Acrophyseter does not appear to have been especially long-lasting (based on the very limited material that we have) and is not known to last up until that late, and the red part is not correct. Boessenecker must simply have been unaware of Pliocene Livyatan teeth, which were published about half a year after the paper you cite. So no wonder, really.

See above.

None of that properly addressed any of what I wrote there.

Yes, Megalodon absolutely outlived all stem physeteriods in prehistory, and the most likely candidate for driving THEM to extinction (assuming biotic factors).

It did? Well that’s fascinating. So I suppose it must still be extant after all, like the fanboys claim, not extinct by or in the late Pliocene, as suggested by the recent peer-reviewed literature.
fossilworks.org/bridge.pl?a=taxonInfo&taxon_no=36728

So am I getting this right, all professional researchers are just biased way too much towards whales to realize the undeniable truth that megalodon ate them all to extinction?

You need to revisit your hypothesis actually. Even Hondeklip Bay was a warm water environment back in Early Pliocene around 5 Ma mark.

The hypothesis stands, the question remains whether it will be substantiated by further data. As I have made clear from the beginning. Preliminary isotope data suggested at least one Livyatan individual primarily foraged at relatively high latitudes. That could (stress is on "could") suggest this taxon preferred colder waters, or it might just be this specific individual. The known fossil ocurrences might (stress is on "might") be the northerly reaches of its range. Or they might not be, or Livyatan might have been globally distributed and we just haven’t found or properly identified the fossils from other regions yet. With over half the known ocurrences of Livyatan having come to light during the last two years, that’s hardly out of the question.

It is not unrealistic to assume that gigantic sharks and stem physeteriods were clashing for supremacy around the world because both CAMPS desired access to same prey items.

You are making this sound as if this were some sort of faction-warfare. We aren’t doing RPGs here.

Since gigantic sharks eventually prevailed in this BIOTIC WARFARE DYNAMIC

BIOTIC WARFARE DYNAMIC? Are you being serious?

, this observation is clearly UNSETTLING to those who have been touting supremacy of marine mammals over sharks on the grounds of seemingly one-sided outcomes of trophic interactions involving killer whales and great white sharks in modern times.As if the suggestion that anything could challenge megalodon isn’t clearly unsettling you. And what do you mean "seemingly" one-sided?

These utterly biased fools completely failed to understand any form of difference between extinct gigantic sharks (Megatoothed lineage) and modern white sharks (Smalltoothed lineage), and the list includes marine biologists as well. Really sad.

So once again, marine biologists are the biased ones? I just want to make sure I understand you correctly, wouldn’t want to run the risk of accusing you of anything you didn’t actually mean.

How is a modern-era baleen whale analogous to ancient stem physeteriods?

You specifically wrote you doubted that there are giant whales with antitropical distributions. A claim that is plain wrong.

North Pole is plankton-rich environment so virtually all known baleen whales are expected to lurk there and/or adapt to those conditions. These are highly specialized marine mammals to begin with. However, baleen whales can inhabit relatively warmer environments.

Well, Bowhead whales definitely don’t traverse the equator…

Ever heard of 'competitive exclusion'?

Yes, so? That doesn’t change that a species range is not simply determined by whether it can kill everything in its environment. That is a view of ecology so simplistic and awesomebroesque I would expect to find it from some kid in youtube comments, not you, an academic, as you say yourself. What gives you this weird idea that all population dynamics are determined by whether a predator would win against another predator in a fight?

You have also failed to address why, following your logic, existence of megalodon was the reason for Livyatan being restricted to the southern hemisphere (something still not based on solid evidence, only vague indications), while they coexisted in the southern hemisphere for several millions of years.

Megalodon supposedly being the "superior taxon" in direct confrontation is an all the more unlikely reason, considering that even using the most conservative estimate for Livyatan, and the most liberal estimate for megalodon, about 80% of all megalodon specimens are smaller than the Livyatan holotype. Yes, most of those are young specimens, but that doesn’t change the ecological aspect of it, that the vast majority of the natural megalodon population would certainly not want to mess with that animal. Therefore that competitive pressure you are talking about is only potentially coming from around 20% of the megalodon population, whereas the reverse would be true for the other 80%.

So if how they would fare in direct confrontation is the determining factor here, how come it wasn’t Livyatan that displaced megalodon?

Yes, Livyatan-types seemingly held their ground in the Southern hemisphere for millions of years (this might be due to abundance of energy-rich food sources in the Southern hemisphere)

And there were no energy-rich food sources in the northern hemisphere, megalodon didn’t need them? So I suppose this means you concede that the reason for Livyatan being restricted to the southern hemisphere (if it was) is in fact the availability of prey, not megalodon?

but they were unable to expand in the Northern hemisphere because BIOTIC pressures were possibly far greater in the Northern hemisphere.

What biotic pressures? Where there more or larger megalodon in the northern hemisphere? Did Livyatan sign a treaty with Megalodon in the southern hemisphere that they would leave each other alone, while it was waging "biotic warfare" against northern megalodons? Sorry, this is getting absurd at this point.

1. Gigantic sharks had a significant presence in the Northern hemisphere (continuous trend) but also encroached into regions inhabited by the Livyatan-types in the Southern hemisphere [most prominent in Late Miocene].

Gigantic sharks had a continuous presence in western south america, likely during the entire temporal range of Livyatan.

There are also Pliocene megalodon teeth from Australia, hence likely sympatric with the Pliocene Livyatan material from there. And this material is way more reliable than an isolated tooth from a fossil seller, there are actual people with expertise stuying it, who seem to agree it is  Livyatan or at least a very similar taxon.

2. The isolated Livyatan cf. fossil reported from the Hondeklip Bay is in a region where Megalodon is absent at this point in time but smalltoothed sharks are present (Govender, 2019).

Ah, so by your logic, the absence of megalodon in this formation would have to be because of competitive displacement by Livyatan, right? After all, you made it clear that you think geographic distribution patterns are pretty much entirely determined by who can kill whom. Your logic, not mine.

Ignoring privately-owned fossil records is not helpful, in a forum-based discourse to say the least.

Then apparently we must refer back to point one:

OK, so what about this, do you count every large Physeteroid tooth as Livyatan now, and if so, how can you not conclude that it was present in the northern hemisphere?

Livyatan is pretty much as cosmopolitan as megalodon then.

How about you drop your focus on the 'average adult size' for gigantic sharks in view of the Carharocles chubutensis-to-Megalodon transitions in Miocene (see Perez et al., 2019)?

No I certainly won’t drop my focus on that. Matching up the largest in thousands of megalodon specimens with the normal adult size of Livyatan would be ridiculous. I am not including C. subauriculatus specimens, only ones referred to C. megalodon, though including the former would be likely to reduce the average size further. I was under the strong impression you already thought me biased enough towards Livyatan as it is, you made it clear that you don’t think anyone in their right mind could not overwhelmingly favour the shark. Now you want me to use a more inclusive taxonomic diagnosis of C. megalodon, to include more, smaller specimens? I don’t get it.

Pimiento et al (2014) and Pimiento and Balk (2015) do not take these transitions into consideration.

Pimiento & Balk even specifically refer to this transition in their paper.

In fact, trying to estimate the 'average adult size' of gigantic sharks from fossil records is also problematic due to long-term pattern of C. chubutensis to Megalodon transitions through much of Miocene (see Perez et al., 2018). This is why one of the shark experts (David Ward perhaps?) pointed out once that gigantic sharks were bigger on average in the Pliocene. Pimentio et al (2015) completely failed to capture this complexity unfortunately. Gigantism is much more elaborate in the Megalodon form in both Miocene and Pliocene.

The average size is pretty much the same, even if only Upper Miocene or only Pliocene teeth are taken into account…

Studies don’t "completely fail" when they don’t get the results we want to see, it is the expectations that were erraneous. Megalodon doesn’t seem to have gotten bigger from the Miocene to the Pliocene. Except possibly if we include C. subauriculatus material in the Miocene record, considering them conspecific (which we possibly should, but that might make this scenario rather blatantly one-sided), in which case its overall average size would go down compared to what Pimiento & Balk, or myself based on their dataset, have estimated.

Otherwise, you need to consider MEAN of Gilbert et al (2018) for potential comparisons with Megalodon because this MEAN was obtained from extensive number of sperm whale teeth.

Gilbert et al did not obtain a MEAN to begin with, because they only estimated the size of the Lee Creek Physeteroids, and actually only the maximum size, and if they had, it would have been the mean of an entirely different physeteroid, not Livyatan. Again, when I want to know the mean size of Megalodon, I don’t take a bunch of Cretalamna teeth instead of megalodon teeth just because they are both lamniforms. When I want to know the mean size of Orcinus, I won’t take the mean size of a bunch of Pseudorca just because they are both delphinids, and when I want to know the mean size of Physeter, I won’t take a bunch of Kogiids, just because they are both physeteroids. What’s next, looking at the holotype of Acrophyseter and concluding that the actual average size of Livyatan was 4 m?

SAM-PQHB-270 diameter = 101.10 mm not Livyatan
SAM-PQHB-265 = 104.46 mm not Livyatan
MML 882 = 74 mm
BAR-2601 = 72 mm
NMR 10227 = 62 mm not Livyatan, and actually 69 mm
NMR 10228 = 85 mm not Livyatan

Diameter of the teeth in Livyatan holotype fall in the 81–111 mm range. However, these teeth are much larger than the isolated teeth on average, particularly in the TH aspect.

+SAM-PQHBB-433 = 93 mm

+SAM-PQHBB-1519 = 80 mm

+Chilean specimen (Loch et al. SVP 2019) with diameter of 109 mm
+Australian specimen with diameter of at least ~100 mm, possibly some bigger than this

The Argentinian teeth referred to cf. Livyatan, BAR-2601 and MML 882, have maximum diameters of 72 and 74 mm respectively (Piazza et al. 2019). The South African cf. Livyatan teeth SAM-PQHBB-433 and -1519 are 93 and 80 mm in diameter respectively, while the Physeteroidea indet. teeth from the same study (SAM-PQHB-270, -265 and -426) measure 101 mm, 104 mm and 68 mm (Govender 2019). The only Chilean tooth we have measurements for is the one studied for the recent abstract by Loch et al. (SVP 2019), with a diameter of 109 mm. The Beaumaris tooth, judging by the picture posted by Erich Fitzgerald on Twitter→ is also roughly 100 mm at the widest portion of the root.

see here: theworldofanimals.proboards.com/post/43747

Diameter of teeth in the Livyatan holotype: ~50 mm to  122 mm with a mean of around 100 mm.

All of these teeth fall neatly into that range, even if we include the teeth not actually referred to Livyatan.
Now tooth size is a ridiculously bad proxy for body size, obviously, so a small handful of teeth shouldn’t be so essential to your argument about body size to begin with, but they don’t even really indicate what you are claiming they do, let alone provide the solid evidence that would justified the firmness of your claims. The tooth sizes of the Livyatan holotype also overlap those of Albicetus, tooth size obviously can be highly variable for a given body size. This goes both ways, of course, owners of an isolated tooth can both be smaller and larger than expected. However it is worth noting that among the most important features of those teeth that suggest their referral to Livyatan is, in fact, their size. If it weren’t comparable to the Livyatan holotype, the teeth would not have even been referred to it. If you want to deduce anything from the sizes of this very limited sample of teeth, then it is that all of them seem to be within the size range of the holotype teeth.

What can you tell about the size of the owner of WH023 as well as the Megalodon that is responsible for damaging/dislodging it?

Relatively little, and I don’t know what that has to do with your Basilosaurus example.

Your disbelief in this regard is not scientifically established.

No it is not, though more so than your belief. But science is not about belief.

But try a thought experiment. Do you think a great white shark (or any extant shark, even a tiger shark, take your pick) could slice through an orca skull? As explained before, meg’s jaws and teeth are about as big compared to a Livyatan skull as those of a great white compared to an orca’s. Now this is not evidence, as if you make the claim that a great white can saw through an orca skull there is nothing I can do at this point to prove you wrong, but it should at least be able to lead to a slightly more informed belief, as I’m sure we can all agree that that’s exceedingly unlikely.

If I highlight the observation of even large whales being literally chomped in half or missing huge chunks of body parts, you will counter with the usual SCAVENGING line-of-thought.

No I will not, I will note that those are not large whales (~1/10th the size of an adult megalodon rather than similar in size) and nowhere near comparable in terms of how massive the bones being bitten through are.

I have seen this video; that blue whale could barely move. Therefore, this analogy falls short in comparison to the case study in focus (i.e. juvenile Megalodon versus a much larger healthy whale).

How do you know how healthy that whale was? It was apparently dead 2 weeks later…

No sign of the Livyatan-types in the Yorktown formation (Govender, 2019).

What are you doing now, wildly citing papers for statements they have nothing to do with?

No of course there is no Livyatan from the Yorktown formation. But you are the one who appears to have the firm belief that an indeterminate physeteroid tooth from Georgia is a specimen of Livyatan. Not that far from the Yorktown formation. I do not make that claim, I was not suggesting at all that a Livyatan killed the Yorktown megalodon, I was suggesting that we could ask this question if we make the claim that a megalodon killed the Livyatan holotype.

By the way, how is my claim unrealistic? What happened to the remainder of the holotype? Ah yes, WH023 represent SCAVENGING, right? Hmm.

Most parsimoniously: yes. What happened to the Livyatan holotype? Are you asking me why fossils are incompletely preserved?

I won’t answer that question here, this will have to wait until I make a post about taphonomy on the basics thread, if creature386 doesn’t do so first.

I am just surprised that 3 decades of studying stem physeteriods have not yielded much in the context of dietary preferences of these animals

And I am surprised that 2 centuries of fossil collecting yielded almost no stem-physeteroids to begin with, but it happened nevertheless. I am also surprised that 2 centuries of studying megalodon have not come up with a (described) specimen with soft tissue preservation yet.

I am not so sure. Livyatan's jaw structure look formidable but its teeth are not efficient cutting tools.

They are not, a smaller whale could conceivably be crushed whole in those jaws. That the teeth are not cutting tools is precisely why the damage may be hard to identify and link to the right culprit. What you described sounded mostly a lot like something simply being crushed by the sheer power of the jaws.

But of-course, dry skull experiments are necessary to gain meaningful insight.

Dry skull estimates would be useful to get an idea of the bite force, they don’t tell us anything about the cutting ability of teeth, but they are hardly necessary that teeth the size, and roughly the shape, of water bottles won’t be cutting much. I am of course aware of that. That is in fact part of the reason for my argument. Granted, if Livyatan had a cutting dentition, its bite could also be confused with those of megalodon. But not having one, the likelihood of a dianostic tooth mark is low to begin with.

I understand but what about TH aspect?

Can hardly be measured in a tooth that is only partially preserved. Like the teeth of Albicetus.

[sam1]

Oct 27, 2019 3:59:23 GMT 5 theropod said:

sam1

source
(Tiger shark, but same principle)


source


source


Shark bites can and do go very deep. Far deeper than just the length of their teeth. Soft tissue compresses under the load of the bite and the jaws go in like a sawblade. A single bite can indeed be devastating. Especially on smaller prey.


But of course shark bites also can and do fail to cause such injuries frequently, especially in larger animals (larger girth=larger gape=less force and less tissue caught between opposing jaws), otherwise scars like these would not exist.

source

Shark bites have awesome destructive power. I could even envision a large megalodon causing debilitating and potentially fatal injuries to even a bowhead or blue whale with one or two bites. At least I certainly won’t call someone delusional for thinking so. Neither would I call someone doubting this delusional.
It is also possible that it would (frequently) fail to do so, due to a combination the high girth and the thick blubber layer. Depends also on the circumstances and how much the whale struggles, living targets aren’t static blobs just holding still to be bitten.
More biomechanical testing would of course be needed to ascertain the plausibility of such a fatal bite, although designing an appropriate experiment would obviously be very challenging. In any case, it is most likely that against large whales, the shark would try to target the part where a first bite would have maximum effect, severing the swimming muscles and large blood vessels in the tail, and come back for more bites if necessary. That does not mean it could bite any body part of any size of whale it wanted and expect to kill it.

Why are you showing these pictures to me?
I was actually thinking to show some of these exact photos to prove my point - that dolphins can survive a full bite on a critical region from a LARGER(than themselves )GWS. 
Larger than themselves.
That first photo shows a dolphin surviving not one, but two of such bites. And that's my point.
A bowhead whale is TWICE the size of a megalodon  and its blubber is far, far thicker in respective to megalodon's teeth than any of those poor dolphins' fat layer was to the attacker's teeth.
Life just can't wrap his mind around these simple facts.