Megalodon size

[Grey]

18 cm long (diagonal), 15 cm wide Peruvian tooth recently auctionned in France.

[Grey]

Not sure about the position but the short and bended crown doesn't look like it was among the large elements of the dentition.



Note the compression fractures due to biting.

[Grey]

A big Chilean 127 mm in width.



The bending corresponds well the the L4 from Hubbell's dentition.

Using the mean of L2, L3 and L4 from Shimada, it suggests 17.8 m TL. Certainly an exceptionnal specimen if true...(sarcasm implied).

[Grey]

[Grey]

139.7 mm wide.

theropod, not interested into the id of this tooth and estimate TL from it ?

[Grey]

Old records report the existence of gigantic teeth.



www.gpo.gov/fdsys/pkg/CZIC-ql638-9-s39-1975/html/CZIC-ql638-9-s39-1975.htm

Case is an author that I know is cited in Kent's 1994 book.

This, along with discussion with European fossil collectors, lets me think personnally that meg teeth even larger than those currently known have been found in the past, but being under private collections were possibly lost or simply unrecorded.

[Grey]

18 cm vertical height. I think the biggest anterior tooth I have seen for now.

[neogeneseamonster]

hello, I'm new here. I read all posts about megalodon and other large marine predators here and I'd like to add some

according to this site, -> www.elasmo-research.org/education/white_shark/teeth.htm

"In 1998, Canadian paleontologist John Clay Bruner presented estimated tooth replacement rates in the White Shark by examining the jaws of 31 specimens, ranging in total length from 4.7 to 15.1 feet (1.4 to 4.6 metres). Bruner's analysis concluded that the average replacement rate of the second anterior teeth differed between upper and lower jaws and between younger and older sharks. He found that in young White Sharks, the average tooth replacement in the upper jaw is about 106 days, while in the lower jaw it was 114 days. Similarly, Bruner found that in older Great Whites, the average rate was 226 days in the upper jaw and 242 days in the lower. The tooth replacement rate of younger White Sharks is probably faster than in older ones because metabolic rate generally decreases with age, thus the tooth-generating membrane forms teeth and grows more slowly in older individuals."

younger shark seems to have almost twice faster tooth replacement rate which can possibly cause bias toward to smaller teeth in fossil record.

[Grey]

I had read it but forgotten the data.

I suspect another reasons slight bias toward smaller sizes in the fossil record.

Welcome by the way, I focuse as well on the large marine apex predators.

[theropod]

The source seems to ba a conference abstract:
"Bruner, J. C. 1998. Tooth Replacement Rate of Carcharodon carcharias (Linnaeus, 1758). ABSTRACT 305. IN: AES 14th annual meeting. Program and Abstracts. Guelph, Ontario. Canada 200 pp. [ABSTRACT]"
There's also an abstract here: www.ualberta.ca/~jbruner/

Since it's designated as a current project there may be more yet to come. Now, it would be particularly interesting to know whether this is inherent to the the juveniles and neonates in question, or whether adult sharks (with adult feeding ecology and tooth proportions) too lose less teeth as they become older.

[Grey]

Regarding the alleged average size estimate of 14 m for adult C. megalodon that some people seem to consider as written in the stone, here are the several points that suggest to take this figure with a grain a salt and being open to the possibility the average size for adults was maybe slightly larger :

We know that Shimada's method based on isolated teeth for megalodon, because of the differences and the decoupled scaling with the white shark dentition, are prone to give underestimates using the most anterior teeth and overestimates with the most posterior teeth.

But looking at Pimiento's matrix we can remark :

- Only A1 and A2 are figured as upper teeth. Because A3 is very small in white sharks, it was not used for megalodon estimates. But we know that A3 is still somewhat smaller than A1 and A2 in megalodon. It is STRONGLY possible that a number of the A1-A2 in Pimiento dataset were actually A3. Hence, even if we can't determine relationship between A1 and body size in megalodon, segregating this position in the range of the possibilities induce a bias toward lower size estimates based on the anterior teeth.

- A1-A2 figures are more prone to underestimates than the lateral teeth range in the dataset (some lateral teeth are ranged in an array as wide as L1-L7). This is a case of "potential underestimates vs potentially accurate ones". The vast number of anterior teeth in the matrix (about 267) could produce a bias toward the slightly lower estimates.

- According to Gottfried and his co-workers, white shark tooth enamel height does not necessarily increase in proportion with the animal's total length. In white sharks longer than about 5 m, tooth size seems to level off at a maximum size independent of further increase in body length. This implies that overall Shimada's method is useful but prone to give potentially conservative results.

- This can raises some doubts that megalodons were mature once they reached 10.5 m like suggested in the original paper.

- Indicated by neogeneseamonster, it appears young Carcharodon loses twice more teeth than the adults. It is reasonnable to expect the same situation in Carcharocles, suggesting a bias toward smaller sizes in the fossil record.

The validity of these points can be checked but for now, they constitute a good reason to not consider the 14 m average figure for megalodon too much strongly.

[Grey]

Sept 24, 2015 0:38:41 GMT 5 theropod said:

Compagno's 1984 regression seems higher than Gottfried's.







French meg tooth, extremely large as it seems to be 190 mm in maximum slant length. An indication that European giants are less often reported than in others parts of the world.

[theropod]

Gottfried, Compagno and Bowman seem to have incorporated Compagno’s unpublished, smaller dataset in theirs:

Using a sample of 175 white sharks at various growth stages with length-mass data (Mollet et al., Chapter 10; L. J. V. Compagno, unpublished data) (Table I), an exponential regression curve (Fig. 4), according to the equation weight(kg)=a[TL(m[sic!])^b], was fitted by the method of least squares, where a = 3.29E-06 and b = 3.174.

Gottfried et al.’s regression represents an update (or Compagno’s 1984 regression represents a preliminary result), hence no including both of them.

Also note that neither of the regressions is actually the precise formula reported in the original paper (though the results only differ insignificantly), the FAO species catalogue cited by Kent states this:

A length-weight power curve for the white shark (96 specimens, mostly from California, and with a total length range from 127 to 554 cm) is as follows:
WT = 4.34 x 10^⁻6 TL^3.14

EDIT: I see what he did there, the difference is due to rounding after the centimetre/metre conversion:
4.34E⁻06*TL(cm)^3.14=4.34E⁻06*(100*TL(m))^3.14=8.2687*TL(m)^3.14≈8.27*TL(m)^3.14
3.29E-6*TL(cm)^3.174=3.29E-6*(100*TL(m))^3.174=7.331552*TL(m)^3.174≈7.332*TL(m)^3.174

The sample size is a miscitation though, it’s 96, not 98

Compagno, Leonard J.V. (1984): Sharks of the World. An Annotated and Illustrated Catalogue of Shark Species Known to Date. Part 1 – Hexanchiformes to Lamniformes. FAO Fisheries Synopsis, 125 (4) pp. 1-249.

[Grey]

Still, Kent doesn't exclude the regression for his estimated weight range for Parotodus, I don't think Kent overlooked that. Simply these are both published equations so they can both be used independantly of the other.

[neogeneseamonster]

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.