Size comparison scale

[theropod]

The point being that we don't know whether the Livyatan holotype was still growing or not. Most of the extant sperm whales used for comparison were well below the average for fully grown specimens too. It's not realistic to assume every adult to automatically be fully grown, as you pointed out yourself.

[Grey]

As far as I remember, sperm whales, while showing various maximum size, have determinate growth, unlike sharks. While Lambert confirmed it as an adult, I think it was fair to assume it was full grown. But you point on something interesting, I already thought that I'd like to see the zygomatic width in larger sperm whales.

[theropod]

Sperm whales have essentially determinate growth, but that doesn’t mean all adults are fully grown. A fully grown adult corresponds to a large specimen in Physeter, we’ve apparently got no indication of that.
See Miller, Brian S. (2010): Acoustically derived growth rates and three-dimensional localisation of sperm whales (Physeter macrocephalus) in Kaikoura, New Zealand. Otago.

[Grey]

But in the case of Livyatan why assuming it was not fully grown ? So far it shows no signs of disease, nor predation...unlike sperm whales in our modern studies which are mostly taken from whaling datas archives and thus were killed before eventually reaching full size.

I'm trying to get Clarke, R. & Paliza, O. Sperm whales of the Southeast Pacific. Part III, morphometry. Hvalr. Skrifter 53, 1-106 (1972) that Lambert et al. used in their study.

It seems difficult to get morphometrics data for sperm whales in excess of 17 m in studies (are they that rare ?).

Interestingly, male sperm whales are sexually mature at 10 m, something similar to what is expected for meg.

[theropod]

why assuming it was not fully grown

For the same reason we are assuming not all of the megalodons were.

It seems difficult to get morphometrics data for sperm whales in excess of 17 m in studies (are they that rare ?).

Yes, they are very rare it would appear.

Interestingly, male sperm whales are sexually mature at 10 m, something similar to what is expected for meg.

yes, they actually have remarkably similar average sizes too based on the studies I’ve seen, and similar maximum sizes as well, despite their different growth model.

I'm trying to get Clarke, R. & Paliza, O. Sperm whales of the Southeast Pacific. Part III, morphometry. Hvalr. Skrifter 53, 1-106 (1972) that Lambert et al. used in their study.

Good luck finding that study, I”ve already searched for it in every conceivable corner of the internet but only found an extended abstract compilation for the whole series.

[Grey]

Using wikipaleo of FB might help to get it.

For the same reasons that we assume some megalodons were not fully grown, I acknowledge this, but the fact marine mammals have determinate growth makes me think that there is slightly more chances that our holotype was full grown. It was obviously not killed by a whaling ship or by a predator and had no disease problem.

Finding solid evidence of a sensibly larger individual could certainly change this though but I'd like to see more data on this.

[theropod]

The morphometrics part would be interesting. Also I was hoping that there might be a few data on body mass, to construct a similar regression for estimating weight.
I don’t think it’s likely that there will be more or larger individuals tough, otherwise Lambert et al. would have certainly included all of them in the data set.

For the same reasons that we assume some megalodons were not fully grown, I acknowledge this, but the fact marine mammals have determinate growth makes me think that there is slightly more chances that our holotype was full grown. It was obviously not killed by a whaling ship or by a predator and had no disease problem.

Perhaps there are slightly more chances, but it remains an unlikely option, because large, physically adult males are really rare in all the studies I can find (perhaps comparable to 17m+ megs). Hence the assumption, awaiting further data, that it corresponds roughly to the adult average.

Anyway, the last comparison definitely showed megalodons that were more than just slightly more likely to represent a big specimen than the Livyatan (over ), I think in any case this is the more accurate reflection of their relative size, and it will be interesting to see it. Let’s see how it turns out.

[Grey]

But aren't we more likely to find an adult full grown Livyatan in the fossil record than physically adults sperm whales that are mostly whaling data in studies ?

I still have a hard time to consider this Livyatan specimen is most likely an average sized, not fully grown adult, especially while supporting the upper estimates. Making Livyatan bigger on average than Physeter and meg well why not, but I'd like to see more indications in that way. In most of the fossil taxa I read about, when there is sufficient data to say the animal was not fully grown, this is reported. Everytime I asked Lambert this, he showed some reservation.

[theropod]

But aren't we more likely to find an adult full grown Livyatan in the fossil record than physically adults sperm whales that are mostly whaling data in studies ?

Firstly, I’m not talking about whaling data. Specifically, I was looking at a report on strandings (there were no physically mature males to be found anywhere). And I recently saw another paper with a larger sample collected from sperm whales measured over a longer period of time that I’ll try to find again.
Secondly, probably not.
Again, how many animals in nature die of old age? Next to none, it’s unlikely that this Livyatan did, just as it’s unlikely that any given megalodon tooth was from a specimen that had reached its maximum growth potential. Just because we have no concrete evidence that it was sick or injured doesn’t mean anything, there’s only the partial skull even available, and even it wasn’t examined for pathology to begin with.

In most of the fossil taxa I read about, when there is sufficient data to say the animal was not fully grown, this is reported.

That’s not the case for animals I read about. Often animals being fully grown is so exceptional it is specifically noted IF any are found or presumed (e.g. Allosaurus, Tyrannosaurus), and the same would be expected for sperm whales.

[Grey]

Let's be clear, I talk about individual full size, not species maximum size.

Regarding strandings, there's justly some conflicting claim here. The abstract about ecology said the holotype was stranded but Lambert said it was found in shallow water layers.

My point is simple, if you find an isolated tooth from even a large sized meg, since sharks grow their whole life (albeit at a slower pace), this is saying that there was a shark that lost tooth and still had some time to grow. In the case of Livyatan we know this fossil comes from an animal that actually died at this point.

As an apex predator, and with no fossil evidences pointing on larger individuals (yet) why assuming this individual was not full grown or close to full size (I mean for itself, not for its species, I obvously recognize there were certainly larger individuals) ?

Take the largest tooth set of megalodon ever found, it is much larger than Hubbell's one (guessing presumably a 14-15 m individual) and since the set of teeth is associated, I certainly recognize this particular meg has most likely reached its full size.

AFAIK when a fossil animal is found, everytime it is established it was not full grown it is reported (Dreadnoughtu...) or when it shows osteological maturity it is reported.

The examination of Livyatan skull was not specifically focused on pathologies but if obvious they would have been reported. To date, there is no indication of disease. But yes the skull is not totally well preserved so...

[theropod]

I understood that, so am I.

I’m not saying the Livyatan holotype necessarily stranded, although it would make sense since it offers an explanation for its death, is known from extant physeteroids and other odontocetes and would be consistent with a primarily pelagic range that explains the rarity of fossil finds and the region it was found in.

I’m not assuming that without evidence because it is not likely, most animals don’t die at their full size, just like most teeth aren’t lost at full size, and in a random sample of fossil physeteroids I’d expect this to be reflected (i.e. the expected value for that sample is not a fully grown male). Since no obvious immature characteristics have been noted I’m assuming it to be socially and ecologically mature, i.e. adult, that’s all.

Dreadnoughtus likely wasn’t just not fully grown (fully grown specimens are known from a small minority of all dinosaurs according to Myhrvold 2013, and this is not explicitely noted most of the time they get described, especially if the descriptions are in Nature), but actually an immature specimen. Especially in dinosaurs, there’s a huge difference. For example, not a single known Allosaurus shows evidence of being fully grown (Bypee et al. 2006), is that noted every time an Allosaurus gets described (rethorical question)?

I don’t see any obvious pathologies on the skull either (though as you say, that doesn’t mean there were none), but if the individual was killed by something I wouldn’t expect to find the pathologies on the skull (If it died in a stranding or of any in a variety of possible diseases that don’t affect the bones, there might not be osteological evidence at all. If it was killed by a predator, osetological evidence will probably be on the tail, flippers and ribcage).

Also why this discussion? As I pointed out we have previously compared animal specimens that were not reflective of the relative sizes of their species and you had no problem with that. This at least comes a lot closer than previous attempts.

–––References:
Bypee, Paul J.; Lee, Andrew H.; Lamm, Ellen-Thérèse (2006): Sizing the Jurassic Theropod Dinosaur Allosaurus: Assessing Growth Strategy and Evolution of Ontogenetic Scaling of Limbs. Journal of Morphology, Vol. 267 pp. 347-359
Myhrvold, Nathan P. (2013): Revisiting the Estimation of Dinosaur Growth Rates. PLoS ONE, Vol. 8 (12) pp. 1-24

[Grey]

Hmm even if stranded, it could still correspond to an old individual. Is stranding necessarilly involving immature/small/not full grown individuals in modern cetaceans ? Though yes, definitive stranding would put further question on this.

I just have a problem with your claim that most animals don't die at their fully size. I obviously refer to adult apex predators. I don't think I need any data here, lions have determinate growth and most adults when they die, die while having reached their full individual size. Why would this be different for Livyatan ?

It also depends of their life, apex predators have violent lives but I think it is secure to say that an adult Livyatan was relatively safe and that it had no issue to keep living and reach its full size. I'm quite surprised you suggest it could have been killed by a predator. I don't think Livyatan to have been very agressive toward its conspecific and I don't think even large megs preyed on a large/full grown individual. And so far no pathology is obvious. The rings in the teeth could certainly help however...

Dinosaurs are certainly not appropriate examples I admit, though I'd say that if each Allosaurus description doesn't mention immaturity it's because of this common trait to the others specimens.

I personnally find this discussion interesting. I'm just saying this particular Livyatan specimen is not necessarilly reflective of the precise relative mean size of its species, unlike the data we have for meg or Physeter here.

I think it would be more valuable to compare Livyatan with the Yorktown Carcharocles tooth set which without any doubt comes from an individual which died at this precise point(and was most likely not dead of predation given its size). The respective situations appear more appropriate to me.

Not saying either that your proposition is not valuable, it certainly is, but I say it's just one interesting comparison among others. I don't think that the various sizes estimates of Livyatan's holotype are most likely similar to the average mean size we have for Carcharocles or Physeter in these studies.

[Deleted]

The most popular dinosaurs of your childhood in a size comparison



About B. excelsus' volume, GSP estimates B. excelsus at ~15 tonnes, which, if he used an SG of ~0.8, suggests a volume of ~18,750 liters. Since GSP's skeletals are pretty shrinkwrapped, the actual volume of a healthy B. excelsus should be somewhat higher, likely above 20,000 liters or so.

[theropod]

You’re raising some interesting points.

Hmm even if stranded, it could still correspond to an old individual. Is
stranding necessarilly involving immature/small/not full grown
individuals in modern cetaceans ? Though yes, definitive stranding would
put further question on this.

Of course not (though, thinking about it, that could possibly be more likely. I don’t recall the dynamics behind strandings to be well-understood though). But it reduces this to a random sample (just like the possibility that a random meg tooth actually belonged to an individual that had reached its individual max size at that point), because the number of individuals that die of old age and are thus necessarily fully grown are likely to be negligible.

I just have a problem with your claim that most animals don't die at
their fully size. I obviously refer to adult apex predators. I don't
think I need any data here, lions have determinate growth and most
adults when they die, die while having reached their full individual
size. Why would this be different for Livyatan ?

Citation needed
I suspect neither of us is an expert on lion growth dynamics, but they can also be presumed to be quite different from those of Physeteroids (I was myself surprised when I found out how relatively rare truly large, mature bulls are, by comparison there appear to be way more fully grown or nearly fully grown lions). Mammals don’t all grow the same way just because they all have determinate growth (that basically just means it stops/slows down to negligible amounts at some point, not when).

It also depends of their life, apex predators have violent lives but I think it is secure to say that an adult Livyatan was relatively safe and that it had no issue to keep living and reach its full size.

If that was the case, then only because it was relatively large compared to potential predators and competitors.

I'm quite surprised you suggest it could have been killed by a predator.

Of course large predators tend to leave each other alone, but extant physeter are also subject to predation. Even tough their ecological role is not the same (obviously), they are also a very dangerous prey. There’s no reason to presume a Livyatan caught in an ambush could not in exceptional cases fall prey to another predator (in this case meaning C. megalodon, and most likely a large specimen at that), especially if C. megalodon, like the great white, occasionally mixed up silhouettes and attacked something not normally part of its diet.

But actually I was only reacting to your suggestion that we should find physical evidence of disease or trauma, which I don’t think is necessarily the case, it’s not that I think this is likely (though not impossible). Actually I would expect physical evidence rather if it died of old age. Think of the westbury pliosaur’s arthritic jaw joint for example.

I think it would be more valuable to compare Livyatan with the Yorktown Carcharocles
tooth set which without any doubt comes from an individual which died
at this precise point(and was most likely not dead of predation given
its size). The respective situations appear more appropriate to me.

Well, I would do that, but as I recall we were pretty much incapable to reach an agreement regarding its size. As I have also pointed out, Shimada’s method gives contradictory size estimates for it dependsing on which tooth we use, so for estimating individual specimens jaw perimeter of toothrow lenght is more reliable (both yield almost the same estimates for the same specimen, so which one isn’t that important), but as you may recall there is the issue of the tooth spacing which we don’t agree about.

I don't think Livyatan to have been very agressive toward its conspecific and I don't think even large megs preyed on a large/full grown individual.

That’s a circular argument, the probability of it being a large or fully grown individual is what we are discussing right now.

Dinosaurs are certainly not appropriate examples I admit, though I'd say that if each Allosaurus description doesn't mention immaturity it's because of this common trait to the others specimens.

Exactly, this is also common in physeteroids.

Not saying either that your proposition is not valuable, it certainly
is, but I say it's just one interesting comparison among others. I don't
think that the various sizes estimates of Livyatan's holotype are most likely similar to the average mean size we have for Carcharocles or Physeter in these studies.

I think that in any case they are quite a bit more comparable than they are to their maximum size, that’s what matters to me.

The sampling methods are different, but as I think predators die at pretty much every stage of their adult life, the error associated with the death vs tooth loss is low. There are likely more Livyatan specimens close to its mean size than there are significantly larger ones (e.g. large mature bulls analogous to 16-18m sperm whales), so basically I expect more fossils of them, the way that is the case with some other large, fossil predators such as T. rex or Allosaurus.

So I’m not saying that these figures are precisely corresponding to each other, but that they are the most similar we have available (more similar than random Livyatan fossil / 1 in 254 megalodon specimen), and based on the assumptions I find most likely (but I will research that a bit more) actually quite comparable.

[Grey]

Of course not (though, thinking about it, that could possibly be more likely). But it reduces this to a random sample (just like the possibility that a random meg tooth actually belonged to an individual that had reached its individual max size), because the number of individuals that die of old age and are thus necessarily fully grown are likely to be negligible.

Now every stranding is not subject to publication and there are certainly stranding from large bulls like this one which was alone while stranded (just like the holotype).

news.bbc.co.uk/2/hi/science/nature/3437455.stm

Plus, the stranding seems not to be clear as I said...

I suspect neither of us is an expert on lion growth dynamics, but they can also be presumed to be quite different from those of Physeteroids (I was myself surprised when I found out how relatively rare truly large, mature bulls are, by comparison there appear to be way more fully grown or nearly fully grown lions).

The lack of large bulls may be due that the papers studying stranded specimens are not that common either. Or simply 18 m bulls are just normally rare ? remember that Ellis (2011) reports that few exceeded 18 m.

Of course large predators tend to leave each other alone, but extant physeter are also subject to predation. Even tough their ecological role is not the same (obviously), they are also a very dangerous prey. There’s no reason to presume a Livyatan caught in an ambush could not in exceptional cases fall prey to another predator (in this case meaning C. megalodon, and most likely a large specimen at that), especially if C. megalodon, like the great white, occasionally mixed up silhouettes and attacked something not normally part of its diet.

But actually I was only reacting to your suggestion that we should find physical evidence of disease or trauma, which I don’t think is necessarily the case, it’s not that I think this is likely (though not impossible). Actually I would expect physical evidence rather if it died of old age. Think of the westbury pliosaur’s arthritic jaw joint for example.

I usually consider adult Physeter immune to any predation excluding humans. Based on this, I even expect less this huge physeteroid to have been preyed even by a potentiall larger, more powerful megalodon. Note that there is still the possibility of not-so mammal specialist diet for Livyatan...

You get a point. I think the best potential material are the preserved teeth that could maybe indicate the age of the animal. But for now between the paper and the various communication I had with several people working on the specimen, I think there is no indication for a disease or predation related death. But of course nothing definitive to say here.

Well, I would do that, but as I recall we were pretty much incapable to reach an agreement regarding its size. As I have also pointed out, Shimada’s method gives contradictory size estimates for it dependsing on which tooth we use, so for estimating individual specimens jaw perimeter of toothrow lenght is more reliable (both yield almost the same estimates for the same specimen, so which one isn’t that important), but as you may recall there is the issue of the tooth spacing which we don’t agree about.

Somehow I had earlier determined what I expect to be the tooth spacing that Siversson used but I could certainly roll with your results which only slightly differ to mines anyway.
Of course jaws perimeter has to be prefered.
Note that students related to the FMHM are actually working on Hubbell tooth set to get a size estimate, in association with Pimiento. Their results will be interesting to us.
I have found some weeks ago an interesting doc which said Hubbell specimen had been estimated at 10.7 m TL but I can't find it anymore...

But yes, I think using the Yorktown specimen could more adequate. It is an adult specimen (unlike Hubbell's) and its associated teeth confirm it died at this point, like Livyatan holotype. And just like the later, I fairly doubt we can infer it died of predation or disease.

Exactly, this is also common in physeteroids.

That full grown status to not be determined in studies you mean ? If so, I disagree, allosaurs specimens are way more numerous. I think it is naturally assumed that adults fossil physeteroids found are full grown or did not have much to grow left. Individually, I don't think why these specimens are not at their proper peak size.

I think that in any case they are quite a bit more comparable than they are to their maximum size, that’s what matters to me.

Yes but that would suggests that Livyatan was larger on average than meg and Physeter and I don't think anything supports this. Jus for now, I don't see the holotype to be the equivalent to the average-sized individuals in meg and sperm whale.

To me that's just an interesting comparison among the previous ones, it allows various perspective. But the lack of quantitative data for Livyatan prevents me to say it is comparable to the results for meg and the cachalot.