Megalodon size

[Grey]

Huge Lee Creek tooth.

[Grey]

It might be possible to derive some TL estimate using Shimada's method. Any guess about its position ?

[theropod]

Pretty sure it's one of the anterior laterals. I don't care much for using this method for individual teeth, but you don't want a precise position, so L1-L3?

[elosha11]

Comparing the tooth sets Grey posted on page 65 and the elasmo.com Megalodon tooth set, I'd guess probably L2.

[theropod]

Speaking of tooth positions, SVPCA was absolutely full of principle component analysis.
It would be interesting to see if this is effective at distinguishing shark teeth from different positions objectively, I.e. whether teeth from the same position cluster together in morphospace, and whether the same is true for isolated meg teeth.

[Grey]

Following this abstract PHYLOGENETIC PREDICTIVE BODY SIZE ESTIMATES OF EXTINCT
SHARKS featured in the SVP 2015.

Are we looking toward future downsizing for fossil sharks, including Carcharocles ?

[theropod]

Too soon to say anything, the abstract doesn’t allow any conclusions, it merely mentions one specimen, and we don’t know all the relevant measurements. I hope we won’t have too long to wait until this gets published properly.

[stomatopod]

Well, there is an abstract that argues that Carcharodontosaurids are more basal than Megalosaurid...

Theropod, one can only hope, I am still waiting for papers that should have been published 6 years ago.

[theropod]

Also apparently chondrichthyans suddenly have a maxilla and a dentary now, or at least dentary and mid-maxillary teeth. Palatoquadrate and meckel’s cartilage didn’t have the right ring to them I suppose.

6 years is nothing, Mike Taylor is apparently still waiting for his own paper that he intended to write 10 years ago→

[Grey]

Plus, the tooth they use for an estimated 13 m TL for meg is 132 mm, assuming they mean vertical measurement, actually such a method is gonna give somewhat higher results than Gottfried's conservative approach.

A downsizing would be very interesting for all its implications (and I'm guessing it could put some of the giant raptorial sperm whales somewhat above in the Miocene marine trophic systems) but this definitely needs to be properly published and tested against the other methods and see the feedback from other fossil sharks experts.

[elosha11]

13 meters for 132 mm tooth seems like a slight downgrade, but since there are a number of examples of teeth exceeding 180mm and even 190 mm, that still may suggest Megs in the 18-19 meter/60+ foot range unless their analysis doesn't predict such increases with the truly huge teeth. Why are they trying to estimate Megalodon's ultimate size using such a (relatively) small 132 mm tooth? Obviously would need to read their full paper, but I wouldn't be surprised to see some significant pushback to their suggestions. It's definitely a minority view at this point.

[theropod]

I think you should wait for the actual implications of this research, which are not clear at all from only the abstract.

It seems like there aren’t any confirmed megalodon teeth that exceed 180cm in height (not slant length), but an estimate of 13m for a 13cm tall specimen would not necessarily appear to be much of a downgrade, of course depending on the exact tooth position (I really hope they will give more details on that part).

[Grey]

I've discussed the abstract with Kent but I'd prefer post his opinion elsewhere. But as suggested by theropod, the strange terminology is doubtful...

[Grey]

Looking at the abstract from Gottfried et al. about megatooth size, 16 m is a conservative figure because white sharks are still growing while their teeth don't grow anymore.



John Maisey has an abstract about a very large xenacanth-like shark, here again he compares the 16 m figure for meg as conservative.



Hastalis size will anyway be known soon :

[theropod]

These fit nicely with the general tendency of maximum sizes being 2-3 times the average adult size and the average weight being just short of 30t.

Can you imagine there are no less than 6 (and probably more) regression equations to estimate body mass from total length in Great White sharks? That’s a pretty impressive number, so I decided to make use of it and included all the ones I could verify.

Regarding maximum size, the mean at 18m is 63.9t, maximum 70.7t and minimum 57t.
At 20m the mean of the regressions is 88.6t, the maximum 98.8t, and the minimum 78.2t.

Methods:
• Average adult _C. megalodon_ of 14m, based on the data set from Pimiento & Balk 2015 and assuming individuals above 11.9m to be adults.
• Estimated size of a large adult, based on a very large tooth (probable upper lateral, 12.6cm wide and 15.8cm tall, with a crown height of 11.9cm) from Denmark that was found in association with some vertebrae (Bendix-Almgreen 1983). The specimen is among the largest in the literature, and certainly the largest that is indicated to have come from a dead shark.
Mean estimates (assuming a position within the anteriormost 3 lateral tooth files) are based on an extrapolated tooth row length and Lowry et al.’s formula (2009, tooth-row length extrapolated for each of the positions and assuming 15% interdental spacing, which I reiterate is not conservative but indeed much higher than what was assumed or indicated by Kallal et al. 2010, Kent pers. comm. or Newbrey et al. in press) and on Shimada’s crown height regressions reported by Pimiento et al. (2010) were congruent in this case.

This also coincides with other estimates that have at various times been the highest in the literature (though currently that title goes to an estimated 17.9m shark reported in Pimiento & Balk 2015), namely the highest figure that based on data considered reliable by Gottfried et al. (1996), and the largest specimen described by Pimiento et al. (2010).

The silhouettes are to scale and centered on their respective mean mass estimates.

Mass estimates were derived from published length-mass regressions (formulae given on graph) for _Carcharodon carcharias_ (Casey & Pratt 1985, Kohler et al. 1995).

–––References:
    Bendix-Almgreen, Svend E. (1983): Carcharodon megalodon from the Upper Miocene of Denmark, with comments on elasmobranch tooth enameloid: coronoïn. Bulletin of the geological Society of Denmark, 32 pp. 1-32.
   Casey, John G.; Pratt, Harold L. (1985) Distribution of the White Shark, Carcharodon carcharias, in the Western North Atlantic. Memoirs of the Southern California Academy of Sciences, 9 (Biology of the White Shark, a Symposium.), pp. 2-14.
    Kallal, Robert J.; Godfrey, Stephen J.; Ortner, D. J. (2010): Bone Reactions on a Pliocene Cetacean Rib Indicate Short-Term Survival of Predation Event. International Journal of Osteoarchaeology, 22 (3), pp. 253-260.
    Kohler, Nancy E.; Casey, John G.; Turner, Patricia A. (1995): Length-Length and Length-Weight Relationships for 13 Shark Species from the Western North Atlantic. Fishery Bulletin, 93 pp. 412-418.
Lowry, Dayv; Castro, Andrey L. F. de; Mara, Kyle; Whitenack, Lisa B.; Delius, Bryan; Burgess, George H.; Motta, Philip: (2009): Determining shark size from forensic analysis of bite damage. Marine Biology, 156 pp. 2483-2492.
    McClain, Craig R.; Balk, Meghan A.; Benfield, Mark C.; Branch, Trevor A.; Chen, Catherine; Cosgrove, James; Dove, Alistair D.M.; Gaskins, Lindsay C.; Helm, Rebecca R.; Hochberg, Frederick G.; Lee, Frank B.; Marshall, Andrea; McMurray, Steven E.; Schanche, Caroline; Stone, Shane N.; Thaler, Andrew D. (2015): Sizing ocean giants: patterns of intraspecific size variation in marine megafauna. PeerJ, 3 (715) pp. 1-69.
    Mollet, Henry F.; Cailliet, Gregor M. (1996): Using Allometry to Predict Body Mass from Linear Measurements of the White Shark. In: Klimley, Peter A.; Ainley, David G.: Great White Sharks: the biology of Carcharodon carcharias. San Diego, pp. 81-89.
    Newbrey, Michael G.; Siverson, Mikael; Cook, Todd D.; Fotheringham, Allison M.; Sanchez, Rebecca L. (2013, in press): Vertebral morphology, dentition, age, growth, and ecology of the large lamniform shark Cardabiodon ricki. Acta Palaeontologica Polonica, in press, dx.doi.org/10.4202/app.2012.0047 pp. 1-65.
    Pimiento, Catalina; Balk, Meghan A. (2015): Body-size trends of the extinct giant shark Carcharocles megalodon: a deep-time perspective on marine apex predators. Paleobiology, 41 (3), pp. 479-490.
    Pimiento, Catalina; Ehret, Dana J.; MacFadden, Bruce J.; Hubbell, Gordon (2010): Ancient Nursery Area for the Extinct Giant Shark Megalodon from the Miocene of Panama. PLoS ONE, 5 (5), pp. 1-9.
    Tricas, Timothy C.; McCosker, John E. (1984): Predatory Behaviour of the White Shark (Carcharodon carcharias) with notes on its biology. Proceedings of the California Academy of Sciences, 43 (14), pp. 221-234.

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