Top Dog

[creature386]

Nobody doubts that a 24 m Physeter would be quite badass, but the condition is that it exists.

[theropod]

And finding something comparable for an extinct taxon is vanishingly unlikely, especially with Livyatan, of which we have only found a single specimen so far. Livyatan is about the size of a male Physeter on average. Similarly, we can say that the largest Pliosaurs were about the size of a female sperm whale.

[elosha11]

I'm not sure about the 24 meter sperm whale. I'm quite skeptical about the length given how much smaller they are today. However, even if confirmed, I'm not entirely sure I would crown it the greatest apex marine predator. Sperms whales really do not demonstrate the aggressiveness or inherent predatory power of a large jawed predator like Megalodon or large pliosaurs. For instance bull sperm whales when confronted by orcas, do not usually demonstrate belligerent behaviour, but rather hang out behind the females or even join the rosette defense formation, a very passive behavior. Obviously a sizable orca pod would be a threat to any single marine predator, but the fact that bull sperm whales are generally so docile makes me wonder about their predatory instincts. They are built for sucking up much smaller, soft bodied prey, not for brutal biting confrontations. Obviously they have ramming potential, but to my knowledge we've really never seen any evidence of them doing this to another animal. They've only done this on stationary ships, and even then only has a rare last resort when being hunted.

In my mind, as long as a 18-21 meter Megalodon is not significantly outweighed by the sperm whale, I would be confident that Megalodon would be the more formidable predator. Not so sure about Pliosaurs, as even at similar lengths, they are likely to be greatly outweighed. And for what it's worth, we've got confirmed Megalodon bite marks on some massive sperm whale bones.

[Grey]

Has someone tried to reach Dino Frey regarding the Mexican specimen ?

I'm thinking we can't definitely discount the possibility of a not adult pliosaur killed by something way larger...

[theropod]

elosha11: A pliosaur isn’t "greatly outweighed" by a sperm whale or lamnid at equal lenght (and hence likely not megalodon or sperm whale record holders either). I’m not sure where the myth of them being so awfully light for a given body lenght came from in the first place, as volumetric approaches clearly disagree with it and they are actually very bulky in built.
Wedel mentioned the largest sperm whale weighed in one piece was an 18m, 53t specimen. P. macromerus scaled to this lenght after McHenry (2009: p. 415) ends up at 55. Lamnid regressions end up at about 65t, but note that these are allometric. Doesn’t look like being greatly outweighed, the pliosaurs, despite being scaled isometrically, are well within measured and estimated masses for the other two.

Has anyone tried to estimate the size of the sperm whale those bitten bones belonged to, and where were they described? As far as I can tell, even bones from a small female sperm whale are gonna look huge.

Grey: No, we can’t, and we never could. The question is how well this has been tested, and without documentation there’s not going to be clarity in that regard. Considering the specimen is not even fully excavated, and several successive publications by various authors have not gone into sufficient detail in that regard, I’m inclined to think the relevant data simply aren’t available, and that personal communication wouldn’t be any less vague at the moment.

[Grey]

I think that Life had estimated a big bitten sperm whale vertebra from a fossil website coming from a 12-16 m sperm whale.

Theropod, you then agree that the possibility remains the Aramberri pliosaur to be not full grown and bitten by a large baleen whale-sized superpredator ?

Yes several publications have not advanced that much but the specimen has to be finally totally excavated, described and named so I think it's worth to ask to one of the authors if the research is still in progress and maybe if they've found more evidences regarding the immaturity of the specimen.

Added with the certain possibility (according to Martill) that this giant isolated tooth in London comes from a ~20 m pliosaur, yes I m wondering if we really can acknowledge 20 m plus pliosaurs as a scientifically valid hypothesis.

[theropod]

I’ve always thought of it as a possibility, considering the specimen is not properly described, and neither were "paedomorphisms" of other pliosaurs, although they had been reported. Increasingly unlikely over the years, although recently it seems to become more likely again, with data on occasional immense fossil bias towards juveniles (e. g. Solnhofen fm.) and some new opinions on the bite mark. But what I’m saying is that we can only get clarity once the specimen is excavated, fully described and measured and the wound has undergone thorough inspection, and that will take time.

There seem to be remains that allow for valid hypotheses on pliosaurs larger than the 13m/20t from McHenry, but they need a lot more documentation before we have a lot to talk about. For example a short description of that tooth and comparison to other large teeth would help a lot. Maybe it would make more sense to write to the BMNH and ask about that, since it should be fully available and not too difficult to describe.

[Grey]

Yes, I ve sent an email to the NHM this week about that tooth but no response so far.

There is also the possibility that thos tooth was not the largest in the dentition but here again we'd need a pic of it.

I fully believe we can valid pliosaurs above 13 m/20 tons likely but in the context of this thread, this is not enough against the largest meg, livy and sperm whales. I m really looking at any hints toward pliosaurs at least 20 m.

[theropod]

That’s fairly speculative at the moment.

[Grey]

What could explain the sheer rarity of gigantics pliosaurs fossils teeth despite they were shed and replaced regularly ?

Sampling bias plus offshore lifestyle ?

[Grey]

Jan 16, 2015 23:19:27 GMT 5 creature386 said:

Nobody doubts that a 24 m Physeter would be quite badass, but the condition is that it exists.

Apparently, this is now considered real, although it may have been rare.

They explain in the paper that soviet whalers may have undereported the sizes of their catch.

Also there are still mentions of bulls up to 27 m long.

BTW, the trailers of the incoming Ron Howard movie about the Essex tragedy with an alleged 26 m bull. Gives a glimpse of the power of an infuriated titan.




(Note : the movie is finally planned for december, not march. Remarkably, Ron Howard's daughter, Bryce Dallas Howard, plays in Jurassic World. The father deals with a giant sperm whale, the daughter with dinosaurs^^).

[theropod]

Not just fossil biases (these affect all animals, to varying degrees of course).
Pliosaurs are thecodont and have very robust, deeply rooted teeth. They probably weren’t lost too often, which suggests both lower tooth replacement rates and a lower frequency of unplanned tooth losses triggering accellerated replacement than in an equivalent shark or lizard. Also it must be considered that these could have been the largest teeth in the dentition, i. e. representing a small part of the total number of teeth these animals had (and being the largest, realistically also the strongest and least likely to fall out).

Pliosaur teeth in general seem way less common than shark teeth for a given time. And I suppose they are more likely to be ignored and hid in some museum basement, because research traditionally, and for obvious reasons, focuses on more complete fossils. So in addition, there's examination bias (e.g. for these supposed giant pliosaur teeth there is not even a picture, while for dozens of giant megalodon teeth there are detailed measurements).

Giant pliosaur fossils in general are of the rare type, not the "vast amount of lost teeth" type (the three biggest pliosaurus species are each known from 1-3 individuals). These are simply not comparable.

[creature386]

Jan 18, 2015 19:53:32 GMT 5 Grey said:

Apparently, this is now considered real, although it may have been rare.

They explain in the paper that soviet whalers may have undereported the sizes of their catch.

Also there are still mentions of bulls up to 27 m long.

Could you please post your sources? And does the source that supports 24 m Physeters say anything about the critique I posted?

[Grey]

I've posted the paper in the opening.

peerj.com/articles/715/

[Grey]

Another view of the thread question.

If we assume that the holotype of any fossil species is in all likelihood in the average size range of the species, then what would be the largest macropredator so far described from a holotype ?

Livyatan ? A perhaps 17 m long average sized individual ?