Not according to grey.
Yes, as I wrote the mount’s ribs are probably too vertical, that gives the chest an even deeper, less streamlined appearance.
Whether I would call
Kogia "streamlined" I don’t know, it appears to me that it simply doesn’t taper much anteriorly because the head has such an extensive soft tissue covering. I.e., it’s chest doesn’t protrude as much it would if you applied a more conservative amount of soft tissues around the skull, as I did for
Livyatan (considering it wasn’t a suction feeder I found it rather unlikely its cranial soft tissues would envelope its entire jaw structure to the extent seen in kogiids).
In a nutshell, one of the best ways for a cetacean to not have an abruptly protruding chest is having an abrubtly deep head. This is what similar soft-tissue assumptions might look like when applied to
Livyatan:
Now obviously, there are other points to consider here too. But simply giving it more flesh below the jaws will make the protrusion (which grey ridicules as a long bone stuck in its chest) much less extreme.
There are further points complicating the direct comparison of body masses.
Is
Kogia perhaps more elongated overall for other reasons than the depth of the chest relative to the skull? Because its spermaceti chamber protrudes well in front of the jaw tip? Because of a proportionately longer tail than in
Brygmophyseter? Because its skull is smaller?
Also, is
Kogia equally wide-bodied, or more laterally compressed?
All these taken into account, there are not many actual data to take from this, but we can remark that
Kogia does appear to have a proportionately deeper chest than for example
Physeter.
The skeletal frame in a living animal certainly tends to be more compacted than in a skeletal mount. I tried to account for that by rotating the ribs backwards.
The question should be whether these considerations can be used to reject the estimate, in which case they should also base on sufficient data to improve it.
He alluded to something regarding the chest being "illusory", but still there has been no explanation on that, months later and after repeated inquiries on my part.
Actually I think there is still a misunderstanding.
Grey claims that my estimate constituted an upsizing of
Livyatan. But my estimate is lower than the only one ever published. This part is really simple. It’s that the statement that I was upsizing
Livyatan is plain wrong, I have done no such thing, and that is irrespective of how bulky I restore it because it’s the body mass that stayed similar to the published figure.
That I estimated the holotype of
Livyatan at 56t, compared to 57t for the published estimate for the same specimen, doesn’t constitute an upsizing under ANY circumstance. The figures happen to be almost identical and they are different estimates for the exact same individual, i.e. they have the same relevance to the size of the species as a whole.
A lower length estimate for this specimen has nothing to do with it. Neither the specimen, nor the species is in any way implied to be bigger due to that (by a slight margin, the opposite is actually the case). If the restoration ends up being correct, all it implies is a shorter and more robust built.
The reference to isometric scaling was because these are exclusively estimates for the same specimen.
A 15.4m
Livyatan holotype necessarily has a different built from a 17.5m one, so assuming that if at 17.5m it was 57t it would automatically have to be estimated at 39t (=57*(15.4/17.5)^3) is flawed. The specimen’s skull stays the same, so clearly there’s no geometric similarity between the two. And more than that, the taxon used as an analogue for making these respective estimates isn’t the same either.
If we are to assume there are larger specimens, those will always be bigger in all those regards. If I were to assume that there are larger specimens and disregard my own estimate, I’d be assuming those would have bigger skulls, be longer and have a greater body mass than the 57t, 17.5m estimate.
But I am not interested in theoretical maximum lengths, they are useless for all intends and purposes. We have one single specimen of
Livyatan, which is all we have to work with.
17.5m compared to 15.4m is a totally arbitrary and irrelevant figure, and you won’t see me extrapolating the mass of a 17.5m version of my
Livyatan model anywhere, grey is the only one who brought that up for reasons I can not even begin to comprehend. That would be the equivalent of extrapolating the mass of a 19.9m version of the 17.5m estimate.
And the assumptions under the published figures would be even higher–if I were to speculate about individuals bigger than my estimate for the holotype by a given percentage, those would be smaller than if I were to speculate about individuals bigger than the published estimate by the same percentage.
I consider it the least biased assumption to treat it as the norm of its species, yes. Until better data comes along. If the only known specimen of taxon A is bigger than the majority of specimens of taxon B, I will tentatively consider taxon A to be bigger.
One could argue I’d be upsizing
Livyatan by assuming the holotype represents a normal-sized specimen…if there had been any previous suggestions that it didn’t, which is not the case.
Regarding the orca bauplan, how come the information leads you to suggest that it is unsuitable for larger sizes? Is it not normal that larger individuals are less maneuverable than smaller ones, irrespective of the species’ built?
I’m sure a 10m megalodon was also less maneuverable than a 6m one, but does that imply its built was limited with regards to size? The current consensus is that it was even bulkier than smaller equivalents such as great whites.
Looking at the link you posted, it suggest male orcas hunt smaller prey along with the females, but may not participate in attacks on large whales due to being less nimble and hence at a higher risk of injury.
Livyatan is not currently expected to have hunted, or even coexisted with, whales as large as, or larger than itself, and if your source is reliable male orcas have no problem hunting smaller prey. Even if it did, there would probably have been no whale that would be sufficiently dangerous to something the size of
Livyatan to require particular nimbleness in its approach (the same can be said for
C. megalodon of course).
Also, since orcas live in pods, the males may be able to afford not participating in such hunts, just like male lions, but that doesn’t have to mean they are physically incapable.
I seem to be unable to see the demonstration that there is anything more limited about the built of orcas than other morphologies such as Great Whites, which even performs very well for them (being among the fastest cetaceans, not to mention the largest raptorial predator in the extant world).