Megalodon size

[theropod]

That a size in that range was not rejected for A. fragillimus either, and it has certainly been proposed for sauropods (check the relevant SVPOW articles!). Scientists seem to be more cautious about sauropods in this size range than about comparable sharks, maybe due to the latter being aquatic species and relatively closely related to some extant species, but it's really off-topic and if we discuss this we should do it here.

[Grey]

250 tons for A. fragillimus has NOT been hinted by scientists, the upper I've read was +150 tons by Armstrong. You're right about the rest.

Yes this topic is about meg size discussion.

[Grey]

I was reading coherentsheaf some post where he expresses his skepticism because megalodon size is far beyond the known data range.

This is absolutely true and like I recalled, the estimates I post based on several methods are possibilities, not absolute truth about the size of one individual to another based on isolated teeth.

Nonethless, we have to keep in mind that there is some consensus about megalodon size today (in excess of 16 meters) and that the uncertainty for the teeth is relative too. A 14 cm wide UA can belong to a shark in excess of 19 m, the same sized tooth can belong to a smaller other individual.

The difference with animals nown by only one piece of fragment (Livyatan, some dinosaurs and sea reptiles) is that we dispose of a number of these different large teeth. From one individual to another, the size within the margin of error can vary.

Anyway, like Brett Kent, I'm not fully convinced yet that meg reached or slightly exceeded 20 m, whereas I'm quite certain for the 18 m mark. But these uncertainties are more related to ecological/physiological issues than to the issues with the different methodologies.

[Grey]

Opinion of MSiversson regarding the doubts by B.W.K about megalodon reaching 20 m.



If we did not have giraffes I am sure people would argue that it could not possibly work have such a tall neck given the very high blood pressure needed to pump blood all the way to the head. There are numerous circulatory novelties in giraffes that enable them to function in spite of exhibiting an ‘impossibly’ tall neck. Nature tends to find a way around physiological constraints. In the case of C. megalodon the dentition indicates TL’s approaching 20 metres. One could of course imagine C. megalodon equipped with a disproportionally wide head. I agree with some of Bretton’s speculations (eg that Parotodus is unlikely to have been a giant thresher sharks as it would indicate tip of the tail velocities exceeding the speed of sound) but I respectfully disagree with him regarding megalodon. The teeth are real and they are huge, there is no speculation there.

[creature386]

Wasn't a similar argument (the one with giraffes) also used on svpow once?

[Life]

Mike Siversson should write articles about Megalodon; a publication authored by him would be wonderful specially. He is extremely well-informed about sharks in general.

[Grey]

He said me he has no manuscript about megalodon in preparation but he's just at now in the middle of a trip with a BBC crew searching for megalodon teeth in Western Australia Miocene deposits. I guess the article or doc will be available in a few weeks or months.

[Grey]

I estimate total length in lamniform sharks based on the total tooth width in the upper jaw (i.e., the combined width of all functional teeth). This gives you a good estimate of jaw size and can then be used to get a rough idea of the total length. Needless to say it works best on species know by associated dentitions (Gordon Hubbell has a seemingly complete associated C. megalodon dentition from Florida). This Flrida specimen can then be used as a template for larger isolated teeth (as long as one assumes that the isolated tooth represent the largest tooth in the dentition, which produces a conservative estimate of TL).

[stomatopod]

May 28, 2013 23:10:29 GMT 5 Grey said:

Opinion of Mike Siversson regarding the doubts by Brett Kent about megalodon reaching 20 m.




If we did not have giraffes I am sure people would argue that it could not possibly work have such a tall neck given the very high blood pressure needed to pump blood all the way to the head. There are numerous circulatory novelties in giraffes that enable them to function in spite of exhibiting an ‘impossibly’ tall neck. Nature tends to find a way around physiological constraints. In the case of C. megalodon the dentition indicates TL’s approaching 20 metres. One could of course imagine C. megalodon equipped with a disproportionally wide head. I agree with some of Bretton’s speculations (eg that Parotodus is unlikely to have been a giant thresher sharks as it would indicate tip of the tail velocities exceeding the speed of sound) but I respectfully disagree with him regarding megalodon. The teeth are real and they are huge, there is no speculation there.

Do you renember the paper that I showed you on Facebook quite a while ago? And why I did comment on it?
We know nothing about the cardiovascular system, but given its evolutionary history it was probably quite derived compared to the ones seen in other sharks. Maybe someone will find a fossilized meg heart one day.
You know who already did find a fossilized Kentriodon brain

Might also interest others: www.escholarship.org/uc/item/2t8325zp#page-3 .
Read the paper starting at page 73. Or even better, read all if you are interested in sharks ;-)

[Grey]

Yes indeed, I was forgetting this.

I think the problem is that Bretton is using the whale shark biology as proxy, because of its size more comparable. I should discuss this with him.

But what can indicate the likelihood of this feature of Carcharodon in Carcharocles ?

[Life]

Megatoothed sharks may have been the most complex sharks (perhaps fish) in history. Greater the size; more penalty it imposes on mobility accordingly. However, this negative consequence is nullified by special biological adaptations.

Megatoothed shark biology is simply not possible without considerable biological adaptations with respect to the environmental conditions. These sharks may have packed adaptations that are not found in modern sharks.

[Grey]

Another analogy was by Chuck Ciampaglio who explained that we could not found either the biological adaptations of the bull shark to live in freshwaters, hinting that we would not found these adaptations if it was an extinct species.

[Grey]

A recently found (May) 6,8 inches meg tooth. They've found also several 6 and 5 inchers.



megateeth.com/blog2010/2013/05/30/our-2013-trip-to-the-nc-ledges-6-8-megalodon-tooth-and-more/

[elosha11]

Ted, could you post all those carnivora pictures of the huge Megalodon teeth found in Peru by Honninger? You also had a great picture of the 19-20 cm tooth with a ruler verifying its length. Those would be a great addition to this thread.

[Grey]

You're referring to that one.



But I suspect it is slightly restored. But depending of how they're restored, they don't necessarily rule out the tooth.

After all Hubbell's tooth too is slightly restored, still this specimen is used as reference :






Based on that tooth, Mike Siversson estimates that the Carcharocles individual behind this reached 19 metres, assuming this is the widest tooth of the dentition, which produces a conservative estimate.



The peruvian teeth :





No confirmation but I believe these are 18 cm or so, I ignore the width.

Others large peruvians specimens.







This famous 18,5 cm peruvian found by Peter Larson (T. rex specialist of the Black Hill Institute) :




Chilean tooth. Mike Siversson estimates it belonged to an approx. 18 metres, 50 tonnes C. megalodon.



That other chilean almost reaching the 17,8 cm (7 inches).




That mysterious tooth that I fail to know the measurements. Sounds huge.



And a reported pathologic huge lateral specimen exceeding 7 inches :