Megalodon size

[theropod]

According to McClain et al. 2015, the average size in a sample of 654 great whites ranging from 0.35 to 7.13m was 3.81m. The equivalent figure from Pimiento & Balk for 544 C. megalodon ranging from 2.2 to 17.9m is 10.02m, or 2.63 times as large.
Female white sharks averaged 4.03, males 3.60m, so by comparison we’d expect male megalodon to average at ~9.47m and females at ~10.60m (so the female is ~12% longer than the male).

Regarding the average size at which sexual maturity is reached, there’s this:

Caillet et al. 1985 said:

White sharks reportedly range in size at maturity between 12 and 14 feet (3660 and 4270 mm) TL (Bigelow and Schroeder 1948, 1953; Hart 1973).

The mean of this range (12-14ft) is 3962mm, times 2.63 that’s a mean length at maturity of 10.42m, with a range of 9.62-11.22. However in their growth curve they listed the size at maturity as 4200mm, which would translate to a mean of 11.05m.
Both are lower than the estimates of 10.5m and 13.3m by Gottfried et al., whose mean is 11.9m

Casey and Pratt cite the same source, but rely on different, unpublished information for their categorization:

Casey & Pratt 1985 said:

Bigelow and Schroeder (1948) estimated the size at maturity to be about 396 to 426 cm which appears conservative from our observations. The one large female white shark (406 cm) we examined had no developing ova, and therefore was immature. Based on the criteria for maturity of 457 cm, the 380 records include 92 adults and 288 juveniles

For our purposes, males and females were considered mature at total lengths greater than 426 cm (14 ft) and 487 cm (16 ft), respectively (Pratt, unpub. data). When data on sex were not available, individuals greater than 457 cm (15 ft) were considered mature.

The latter gives us ~12.02cm (male 11.22m, female 12.83m), just insignificantly (~1%) higher than the mean of Gottfried et al.’s estimates (certainly insignificant if you consider that males are alledgedly more common).

There is some contradiction as to what size great whites mature at, but Gottfried et al.’s numbers, that formed the basis for the 14m adult average, seem reasonable. There’s no bias towards smaller size on account of the size estimates at maturity that were used.

neogeneseamonster:
7-8m great whites are virtually unheard of, and I don’t think there are any reliable data on any such specimens, so I’d say their impact is negligible. But what you describe will probably counteract the trend of young sharks to lose more teeth, if indeed that trend exists among adult sharks.

–––References:
  Cailliet, Gregor M.; Natanson, Lisa J.; Welden, Bruce A.; Ebert, David A. (1985) Preliminary studies on the Age and Growth of the White Shark, Carcharodon carcharias, Using Vertebral Bands. Memoirs of the Southern California Academy of Sciences, 9 (Biology of the White Shark, a Symposium.), pp. 49-60.
  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.
  Gottfried, Michael D.; Compagno, Leonard J.V.; Bowman, S. Curtis (1996): Size and Skeletal Anatomy of the Giant “Megatooth” Shark Carcharodon megalodon. In: Klimley, Peter A.; Ainley, David G.: Great White Sharks: the biology of Carcharodon carcharias. San Diego, pp. 55-66.
  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.
  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.

[neogeneseamonster]

yes, I also thought the numbers were highly doubious(Since no scientifically verified 7-8m white shark is known today). So my main point was the overall trend of growth rate(shape of graph).

[theropod]

I’ll try to find and look into that study you cited for the graph.
The only one I know about great white shark is from 1985 and bases on a very small sample, so that the shape of the growth curve itself remains quite uncertain. It’s probable that it looks similar to shown in the graph you posted though, smaller sharks growing more quickly than larger ones (being pretty much the case in all animals).

So yes, a hypothetical great white that lives out its entire lifespan spends disproportionately more time of its life at relatively larger sizes, compared to the relative frequency of such large sharks (evidently very low), so sharks that grow particularly old may bias the tooth-record upwards compared to sampling living individuals. Possibly an explanation for the slightly higher than expected number of really large specimens, if that isn’t just statistical noise.
In exchange it may lose teeth at a higher frequency at smaller sizes (at least as a juvenile, and I could imagine that this is partly because it is growing more quickly, hence for the same reason (It’d also be a good question how the dietary transition to mammal-based feeding figures into all of this though. Only future research will tell).
We’ll have to see about that. There are always potential biases in either direction, we just shouldn’t be too ready to assume any particular overall bias without proper evidence.

[Grey]

Considering Gottfried et al. indication about stopped growth of enamel/tooth and Kent's suspicions toward decoupled scaling, from this standpoint it is understandable to consider the current published size estimates of Megalodon based on regression equations as reasonnably cautious if not conservative.

However I don't dismiss the work in preparation using phylogenetic factors for body size estimates. Campione is involved in it (but Terry Gates is the project leader), he said the work is very much at infancy so he couldn't compare it with current sizes estimates.

[Grey]

Oct 21, 2015 21:03:42 GMT 5 neogeneseamonster said:

Grey: nice summary

to add more about bias-causing factors, I think growth rate pattern of lamniform sharks can also cause some bias in fossil record.

Source: Cailliet, Goldman and Mollet. 2014. Using demographic analysis to assess the population size of shark species: a test using the White Shark (Carcharodon carcharias) sub-population off central California, USA

from: briantissot.com/2015/07/06/the-search-for-monster-great-white-sharks/

since sharks grow very rapidly when they are young and slowly when they are old, I suspect older sharks may have more time to lose their tooth.

for example, according to the graph above(though it's number on y axis is highly doubious), the great white sharks are in 7-8m range for almost 40years. While they are in 3-4m range only for about 5years. Therefore, IMO, this may cause bias toward larger and older indivisuals.

However, I think this factor may only cause minor(or no) impact because rarity of large and old indivisual(especially in shallow water) will make this virtually meaningless.

Regarding Megalodon, I think Pimiento said it is hypothesized to have lived up to about 100 years old.

[stomatopod]

I think the average size for mature GWS is higly dubious and I personylly think that 4.5 meters is a good starting point for females, which agrees with what we know from recorded specimens.

[Grey]

Apr 5, 2015 2:18:30 GMT 5 Grey said:

Update, after some doubts, this tooth has been confirmed as genuine by various collectors and the author of the picture.

So far, one of the largest, if not the largest, Megalodon tooth recorded.

[elosha11]

A real 8 inch tooth. Amazing. Where was this tooth found, South America? I assume it's in a private collection and the owner wouldn't be inclined to share with researchers for official measurements.

[Grey]

It's a Peruvian tooth.

Actually it seems it is a little more than 190 mm (the cast of it is that size) and 148 mm wide but this certainly needs to be confirmed as casts are not necessary perfect. That's a potential 8 incher.

It's a Peruvian tooth.

But I have contacts researching about giants in France. In the previous page, I have posted a French tooth seemingly 190 mm in slant length (but more slender than this one).

[Grey]

I said previously I regularly see very large megalodon teeth from private collections here and there. Actually quite frequently and I don't take the time to post all of them.

Nevertheless, here are some examples which I use to get body size estimates using Shimada's method. I use the ranges available in Pimiento's matrix. Being unsure of the most adequate range, I use several possibilities for them. I exclude the range where most of the teeth are far too much different than the tooth. I also exclude the ranges yielding totally unreasonnable figures.

This tooth from South Carolina is particularly huge regardless of the position, quite clearly a Lateral. The CH seems to be about 109 mm, give a mm or take it.



L1-L3 : 15.39 m

L1-L5 : 18.84 m

L1-L3, l1-l3 : 18.86 m


If anyone prefers another range he can propose it.




This one is Chilean. 83.8 mm wide, 57.7 mm CH.

L3-L6, l3-l6 : 21.25 m

L5-L7, l3-l6 : 23.49 m

I can't see another range where the teeth look like this one but it is possible I have missed one. But this tooth seems indeed very large for where it belongs in the dentition.




A huge Chilean, 149 mm wide. But I really can't say a range looking at it.


I've seen comparable specimens in the collections I follow.


Objectively, I think this demonstrates the 18 m maximum size for C. megalodon using Pimiento and Shimada's data is probably conservative. Specimens estimated over this appear to be expectedusing the methodology.

[elosha11]

Grey, I too think 18 meters is probably a conservative maximum length. Apparently, you are following Shimada's methodology to predict sharks from 18.8 up to 23.5 meters long, in your first two pictures. It is noteworthy that Pimiento, et al's study's largest tooth was an upper lateral of "only" 41.2 mm in CH and 37.6 in CW, predicting a shark of 17.9 meters. Your teeth appear to have a much greater CH than that.

Using Shimada's method, can you predict what the crown height would be for an upper anterior in a matching set with the two referenced teeth from which you provided estimates? And do any upper anteriors exist with such a crown height corresponding to 18.8 to 23.5 meters. What I'm trying to see is if we have any examples of other types of teeth besides laterals which would yield such length predictions using Shimada's calculations. Not sure I'm comfortable with sharks 22-23 meters long, but I could see the max size at perhaps 20 meters, 21 at most.

Have you ever contacted Pimiento, Ehret, and the others from the 2010 study and showed them these type of huge laterals? While I doubt they'd give an official prediction, they might informally back up your claims to lengths well exceeding 18 meters.

[Grey]

Note that Pimiento rather uses a range of possible positions rather than a single position, which avoids over and underestimates in the extrapolation given the differences between the dentitions of megalodon and the white shark.

I don't have huge faith in these figures I used, maybe I've use wrong placement or missed another one, especially for the 23 m estimate. But I couldn't find another appropriate range of position for that tooth so who knows ? The purpose is rather to suggest that 18 m may not be the absolute upper limit deduced from this method, widely used currently in professionnal research.

The CH for the corresponding upper can be predicted, I've did it earlier for other teeth in some cases the CH for the upper suggests larger UA than those actually reported in fossil collections. It can be deduced either that it is an overestimate but an alternative possibility is that UA larger than those (reported) in collections may occure or may have existed in some extremely large sharks; if anything, it is well possible that from all the megalodon teeth found anywhere in the world, the one indicating the largest individual shark ever is not represented by a large UA but by a smaller, less remarked, tooth from the dentition. It is also possible that the corresponding uppers, in some cases, would be somewhat shorter than normally deduced (individual variation).

I may have tried to discuss the size extrapolation from huge lateral or posterior teeth from private collections but never got a clear response, I think the researchers don't have time to examine each private tooth, especially only on a computer screen rather than direct examination of the specimen.

But I plan to ask it though.

Basically, I'm quite sure that these specimens above are way bigger than any measured by Pimiento in her matrix. But again, it's not published so it remains merely indicative. Using the current 18 m figure is still reasonnable.

[elosha11]

Thanks for the explanation. I wish some of these private collectors would just let scientists borrow their Meg teeth to make better estimates. It's quite plain that the largest teeth in collections have never been subject to scientific scrutiny, which again may cause a bit of an underestimate in size. I'm comfortable with the consensus that Megalodon reached 18 meters/60 feet, but in reality I think the shark probably could reach 65 feet or a bit more. Obviously, those would be exceptional individuals and not the "average" size adult (however average is defined), but I surmise that such a huge 18+ meter shark would be akin to an 18-20 foot great white. Very large and uncommon, but not really all that rare. Especially without the pressure of mankind, apex predators are free to live and grow unencumbered.

[Grey]

I try to extrapolate TL using CH method from several teeth specimens recently described in the litterature.

Estimated total size for the shark possessing the tooth found last year in Spain and recently described here : www.biodiversidadvirtual.com/taxofoto/sites/default/files/first_description_of_a_tooth_of_the_extinct_giant_shark_carcharocles_megalodon_agassiz_1835_found_in_the_province_of_seville_sw_iberian_peninsula.pdf



Identified as a lower left anterior, so a1-a2 or a1-a3. CH 93.5 mm, suggests a Megalodon about 13.2-14 m long that once roamed in our Mediterranean sea (for the European members...).


Three specimens described from Portugal here : ddd.uab.cat/pub/geoact/geoact_a2015m9v13n3/geoact_a2015m9v13n3p181.pdf

The largest of the three comes from a large specimen.



There is discrepancy with the scalebar so I use the measurements in the description. The CH, if complete, would have been around 87.3 mm. They tend to assign this tooth as a l1.
Using solely this tooth position, it seems to suggest a 15.3 m Megalodon.

Using the l1-l2 range used in Pimiento's matrix (the nearest range to the assigned position by the authors for this tooth), it suggests a Meg about 16.2 m.

The second tooth is in a matrix of rock but enough complete. The assign it as a l2.



Using solely this position, the crown height seemingly about 43.2 mm, it indicates a TL about 8.3 m.

Using one of the proposed range from Pimiento's matrix, I get 8 m long for l1-l2, and about 8.8 m long for l1-l3.

About this particular individual they say in terms of size, it could be compatible either with a rather archaic M. megalodon shark, late Early to Middle Miocene in age, or to a Late Miocene or Pliocene one from a very young individual.


The last tooth is heavily embedded in matrix and the photo doesn't allow a secure measurement.



In order to be conservative, I'm gonna use the middle crown height measurement they report as 46.1 mm (precisely and "probably somewhat higher").
They report the specimen as a 4th or 5th lateral mandibular tooth.

Using solely the l4 position : 15.7 m long.
Using l5 : 24.7 m (?).

The middle of the two position being 20.2 m.

However using the range of l1-l5 in the 2015 matrix suggests 13.6 m. Although, again, the measurement I've used from the tooth is probably undersize and the l1-l3 positions in the range I used probably the size even more toward a lower figure.

Either the authors didn't notice how large is that tooth for its would be position (and how large would be that Megalodon individual) or they have made a mistake about the position.



Tooth described from Japan here : www.researchgate.net/profile/Yuji_Takakuwa/publication/275036943_On_a_shark_tooth_remain_collected_in_the_Gunma_Safari_Park_Tomioka_City_Gunma_Prefecture_central_Japan.%28in_Japanese_with_English_abstract%29/links/553091630cf20ea0a06f8125.pdf




The tooth is incomplete and is reconstructed.

CH approx. 96 mm. Identified as a lower third or fourth (a3 or l1).

Both positions produce an almost identical result, approx. 16.8 m long.

Alternatively, a range from Pimiento's matrix including one of these positions can be used.
a1-a3 suggests 14.4 m.
l1-l2 suggests 17.8 m.

So using the available scientific methodolgy, this particular Megalodon was somewhere between 14.4 and 17.8 m.

Three teeth are described from Chile here : www.researchgate.net/profile/Jaime_Villafana/publication/283285140_Late_Neogene_Elasmobranch_Fauna_From_The_Coquimbo_Formation_Chile/links/5633481708aefa44c369dd1b.pdf



Here again, some discrepancy between the scalebar and the size measurements in the text. I've rather relied on the text indication. Given the eroded state, I've focused on the second specimen MALS P-6564.

The CH seems to be approx. 66 mm (quite tentative). Identified as a lower lateral, its shape certainly excludes l1, l2 and l3. From l4 it seems plausible. However using solely l4 suggests a 22 m plus figure.
To avoid overestimates, I propose a range of l1-l5 using Pimiento's matrix.
Suggesting approx. a 19.1 m shark, keeping ind mind l1, l2 and l3 respective shapes doesn't reflect it, so perhaps a bias toward smaller size.
In short, maybe an indication of 20 m or so TL.

It really seems that Chile was home to a particularly large-sized population.

[theropod]

est. 91mm tall, 72mm wide (root) with a crown height of ~71mm
The preserved portion of the crown has a maximum labiolingual thickness of ~16mm.

As regards the position, when comparing the slant of the preserved crown to the teeth figured by Uyeno et al. 1989, it is an excellent match for the tooth figured in pl. 6(a), and that is what the outline bases on.
Can anyone here read Japanese?

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