Megalodon vs. Livyatan melvillei

[coherentsheaf]

I think to clear up the difference we would need simulations. Hydrodynamic differences of this sort are nontrivial. That could be a quite comprehensive Blender Project where you would need to hardcode a lot of stuff theropod.... Maybe ask a professor wheter you can do it as seminary work.

Edit: Anyway, we would need to look in the posibility that we also have eolutionary pressures at work here, after all pliosaurs had more cartilage apparently, so likely it is maybe possible for whales to do so as well. Do they? If no, to what extent are there very stiff sharks? It could tell us something, when we compare stiff sharks to non stiff ones, or stiff whales to non stiff ones, so they exist.

[theropod]

^Well, sounds great, but I really don’t have the python skills. My abilities with blender never went past modelling fairly simple shapes. But yeah, we’d need simulations.

[neogeneseamonster]

Regarding "explosiveness," maneuverability and stamina, it seems we do not have very clear evidence at least for now. As far as I know, this problem isn't so simple.
First regarding 'explosiveness', one can expect sharks are more explosive than odontocetes because shark's body is very muscular and most of their muscles are white muscles.

www.elasmo-research.org/education/white_shark/muscles_jaw.htm <-ref

Here, the author says "Something on the order of 85% of a 'typical' shark's body weight is muscle." However, I'm not sure if it is really acurate since there is another page that says about 15% of a 'typical' shark's body mass is a liver(some sharks have larger liver. For example, a basking shark's liver is 25% of total body mass. So the number vary). Still, an expert in "shark attack survival guide(shark week 2010 series)" also said that about 70% of shark's body is muscles and this number seems more plausible(if we assume that a liver takes about 15% of shark's body mass and muscles thake 70%, there is extra 15%).

Anyway, whether or not the number is 85 or 70, that is pretty high percentage.
Here is another source: Physiology of Elasmobranch Fishes: Structure and Interaction with Environment-Robert E. Shadwick,Anthony Peter Farrell,Colin J.
This book gives lots of informations about shark's muscles.

According to this book, sharks cannot control white muscles as finely as teleosts can do and white muscles are either on or off, making shark's change in activity more dramatic.
Here another part of the e-book:

So as in many other animals, shark's white muscles give faster and possibly, more power compared to red muscles(at least in a limited time period).
Lastly, since megalodon was a gigantic shark, I tried to find out if size affects muscle power as it is in some animals.

Interestingly, unlike in terrestrial animals, shark's muscle power does not inversely correspond to size increase. On the other hand, this book also implies that larger sharks have significantly slower red muscles.
In short, there are 4 points we can think about megalodon's explosiveness. These are :
1. Large portion of shark's body is muscles(70% or perhaps 85% though it is not certain).
2. Most muscles in shark's body are white muscles, which is faster and produces more power(in short time) than red muscles.
3. Larger size does not mean weaker muscles(pound for pound, of course) unlike terrestrial animals(though the red muscles are slower).
4. Since sharks can not control their white muscles finely(on or off) and have notably slower red muscles, gap between 'normal speed(using red ones)' and 'burst speed(using white ones)' may be more pronounced. 



ps. According to this -> www.nefsc.noaa.gov/publications/tm/tm110/tm110.pdf paper, Carcharodon carcharias' liver is about 15-20% of it's body.

[Grey]

coherentsheaf

I d like to read more data about the amount of carrilage in large pliosaurs. I ve not read anything about that since Buchy's thesis.

But if anything, it doesn't seem to me that it occures at all in odontocetes.

Though, perhaps if we only have found the skull of Livyatan it would be because his skeleton was more cartilaginous?

Is the tendency of very large animals to not be preserved well is more frequent for marine than terrestral taxa?

[neogeneseamonster]

Here's some data about cetacean muscles.
"Fibre-type composition varies widely between muscles, in accordance with their functional requirements. Marine mammals that regularly perform deep, long-duration dives have locomotor muscles mainly composed of large type I fibres4 containing elevated myoglobin (Mb) concentrations. A novel myofiber profile for diving mammals, characterized by a muscle composition of ~80% fast-twitch (Type II) fibers with low mitochondrial volume densities, has been recently described in beaked whales5. Thus, there is a wide array of muscle adaptations for breath holding and apneic underwater diving."
ref -> www.nature.com/articles/srep15909

Unlike sharks, most marine mammals' muscles are primarily red muscles(albeit the notable exception of beaked whales described above). Likely due to their need for oxygen storages. The red muscles gives great stamina and perhaps, along with other factors(such as being warm-blooded), this is the reason why 'swimming' whales look hyperactive when compared to 'crusing' sharks.

However, as stated above, beaked whales have remarkably differnt muscles(white muscles comprising 80% of all muscles) and this cannot be ignored.
Therefore, it is hard to speculate what type of muscles Livyatan had. If Livyatan had more red muscles like most marine mammals, it would have had greater stamina but less explosive and less powerful(within short time) muscles than megalodon's. Conversely, if it had something like beaked whale's muscles, we can't easily compare since both animal's muscle would have been more similar to the other.

[neogeneseamonster]

I'm curious if there is any data that explains how much of a 'typical' dolphin's body is muscles. Since we do know some advantages and disadvantages of both shark's and whale's muscles, such data will be very helpful!

[theropod]

^I’m not sure how meaningful that is without a figure for a sperm whale or killer whale (understandably difficult to get), since relative muscle masses can differ strongly between close relatives (and are probably heavily dependant on ecology). But here you go: jeb.biologists.org/content/jexbio/202/3/227.full.pdf
In 3 adult Fraser’s dolphins its 56-59%, in a Spinner dolphin 52%.

More solid data for a shark (i.e. from someone who actually dissected and measured one) is certainly required though. To be honest both those figures sound more like people are just throwing around with all sorts of wild guesses. A source stating 85% of a shark’s body is muscle, and upwards of 15% is liver is rathery funny than anything else. Even with the 70% muscle mass from the documentary, what remains for every single non-muscle, non-liver component of the body (skin, skeleton, other organs…) is very small. Certainly it would be better to rely on scientific data rather than rumours.

The data on muscle composition are very interesting though!

[neogeneseamonster]

Well, I do agree that we need more species-specific data on both sharks and whales and I too think the number(the muscle percentage) they gave is not much more than rough 'estimate'. However, I don't think the number is completely baseless rumours. Slightly off topic, but the paper I've posted above actually give more data on shark's liver mass so you can look up(in case of the great white, the number is 14.6-22.7%). In addition, though the 70% 'estimate' needs more written data to be sure, it isn't completely out of sense since shark's body parts other than muscles(and some associated soft tissues) and liver only take little part of a shark's total mass at least in case of some sharks. For example, according to this( -> pubman.mpdl.mpg.de/pubman/item/escidoc:2241221:2/component/escidoc:2241954/2241221_.pdf ) paper, only 6% of a bull shark's wet body mass is it's skeleton.

Anyway, good points and I will try to find more rigorous and species-specific data on this ^

[elosha11]

^ With regard to the comment above, I think it's well known that a cartilaginous skeleton would be lighter than a comparably sized bony one, particularly those of a large cetacean. I don't know if 6% is a fair representation of the weight of other large shark skeleton's but it isn't a number that surprises me. The thing we all know about a large shark's skeleton is that they become heavily calcified, hardened, and in practical effect, as functionally durable as bone. (Of course, such calcification in large sharks has trade offs, and likely contributes to overall decreased flexibility. You won't see a great white twisting its body into almost a "U" shape, like much smaller sharks can do). So an overall lighter skeleton does, in theory, permit more of the shark's weight to be made up of muscle and liver.

I have heard whale skeletons are very heavy, but I do not know what percentage of a whale's total weight is comprised of the skeleton. Anyone have any info on that?

[elosha11]

Jul 19, 2016 20:44:28 GMT 5 theropod said:

^I’m not sure how meaningful that is without a figure for a sperm whale or killer whale (understandably difficult to get), since relative muscle masses can differ strongly between close relatives (and are probably heavily dependant on ecology). But here you go: jeb.biologists.org/content/jexbio/202/3/227.full.pdf
In 3 adult Fraser’s dolphins its 56-59%, in a Spinner dolphin 52%.

More solid data for a shark (i.e. from someone who actually dissected and measured one) is certainly required though. To be honest both those figures sound more like people are just throwing around with all sorts of wild guesses. A source stating 85% of a shark’s body is muscle, and upwards of 15% is liver is rathery funny than anything else. Even with the 70% muscle mass from the documentary, what remains for every single non-muscle, non-liver component of the body (skin, skeleton, other organs…) is very small. Certainly it would be better to rely on scientific data rather than rumours.

The data on muscle composition are very interesting though!

You would think that as popular as orcas are, and as many have been kept in captivity (for better or worse), there would have been dissections and scientific studies of specimens to determine such things as muscle percentage and other basic anatomical information. It would be understandably more difficult with truly gigantic animals like the sperm whale. Has the show "dissecting nature's giants" ever studied an orca or a whale?

[theropod]

Well, obviously ordinary cartilage is far less dense than ordinary bone, but ordinary cartilage is also not a functional skeletal building material in a large animal, so the obvious question would be whether to approximate the mechanical properties of bone, a cartilaginous skeleton wouldn’t also have to approximate its density (or at any rate, weight, with an increase in diameter).

You mean "inside nature’s giants"?
They did dissections of both a sperm whale and a fin whale, as well as a great white shark (no orca though), but they didn’t seem to collect any data on muscle percentages. And slicing up even the shark completely and measuring its muscle mass would be a lot of work, needless to say it’d be pretty much impossible to accomplish with a multiton whale in the field.
Also there would be a massive amount of fluid loss during the dissection that would be very hard to take into account properly.

[spartan]

As for the body composition of the sperm whale, according to one study they have a muscle mass percentage of around 34%, 33% blubber, 10% bone and 9% intestines.

www.researchgate.net/publication/240590693_Body_weight_of_some_species_of_large_whales

The general trend seems to be that the rather slow moving whale species have less muscle mass (these are mostly the whales that are classified as "fight species" in regards to their defense stragetgy against orca pods) than the fast moving ones ("flight species").
The Minke Whale even has among the highest muscle mass percentage of any animal I know of, with 62% (the highest verified are from the Skipjack tuna and the Rainbow trout, topping at 67-68%, if anyone's interested).

[elosha11]

^Interesting. That's almost counter-intuitive; we'd probably think a more "muscular" species would be more likely to fight, but if your sources are correct, the whales with the highest musculature of modern cetaceans belongs to the "flight" species. Which actually makes sense, they would need incredible strength and stamina to move their massive bulk in extended flights from orcas (or other extinct macro-predators), but they have neither the instinct nor weaponry to be inclined to fight their attackers. On the other hands, more massive and bulky whales, such as bow-heads or grey whales, I assume have more blubber and less muscle. Which also makes sense because they probably can more easily endure attacks with higher blubber content, which may give them time to fight off/deter their attackers with tail swipes.

Of course this doesn't entirely address what percentage of muscle was obtained by either Livyatan or Megalodon. I don't see either of these animals as having the endurance of an orca pack, able to sustain high speeds for long distances. But, I think it likely that each were capable of bursts, even sustained bursts of speed to ambush prey, or even give relatively short chases. Of course, the large, speedy rorquals were far more rare and did not apparently appear until the latter part of Meg and Livy's existences. It is an interesting question whether rorqual's body type and swimming speed evolved as a response to Meg and Livy, or in response to the growing orca (and perhaps smaller toothed sperm whales) threat, or whether it was a combined response to all of these predators and other environmental pressures.

[jhg]

Aug 12, 2016 21:02:16 GMT 5 elosha11 said:

Of course, the large, speedy rorquals were far more rare and did not apparently appear until the latter part of Meg and Livy's existences. It is an interesting question whether rorqual's body type and swimming speed evolved as a response to Meg and Livy, or in response to the growing orca (and perhaps smaller toothed sperm whales) threat, or whether it was a combined response to all of these predators and other environmental pressures.

I myself never thought of that before.

[neogeneseamonster]

Very interesting point elosha11. I wonder if rorquals reached their gigantic size in response of both extinction of meg(and possibly Livy) and rise of orca pack. It's based on simple logic. When megalodons and giant sperm whales were present, larger size probably wasn't an advantage because larger size can not protect themselves from already much larger predators. However, after demise of megalodon and Livyatan, such disadvantage of being large probably diminished and as orca pack became deadlier, larger size may have turned into an advantage since killer whales are not mega-predators like meg and Livy. Which means the larger the whale is, harder for an orca pack to kill it.
This idea has some speculative premises, but I think we can consider both orca and meg possible evolutionary drivers of rorqual's gigantic size.