“Recent” Otodus megalodon teeth

Challenger sharks

Shark teeth recovered from the Pacific Ocean by the HMS Challenger.

The megatooth shark Otodus megalodon was recently estimated to have gone extinct in the early Pliocene c. 3.6 Ma (Boessenecker et al. 2019). Despite this, there have been persistent reports of O. megalodon teeth from the late Pleistocene-Holocene. These have been used by cryptozoologists as evidence to speculate on the survival of O. megalodon in the modern day. It has long been recognized that the teeth were misdated using invalid techniques, a fact often disregarded by these same cryptozoologists. Contemporaneous fossils reliably date them to the Miocene-Pliocene within the accepted temporal range.

The most well-known claim of recent O. megalodon teeth was made by Wladimir Tschernezky in 1959. Tschernezky analyzed two teeth dredged from the seafloor near Tahiti by the HMS Challenger expedition in 1875. He attempted to date these teeth by measuring the layer of manganese dioxide that had accumulated on them. The first tooth had a maximum MnO2 coating of 1.7 millimeters while the second had a maximum of 3.64 millimeters. Assuming a minimum growth rate of 0.15 millimeters per 1,000 years, Tschernezky calculated the first to only be 11,333 years old and the second to be 24,206 years old1. However, his methodology and therefore results are completely erroneous.

Belyaev and Glickman (1970) provided a rebuttal to Tschernezky’s analysis. They noted that Tschernezky had used a MnO2 growth rate based on prior radium dating. Dating manganese nodules using radium was found to give a growth rate 20 to 30 times greater than the more accurate ionium-thorium method. Thus the age incorrectly appears to be significantly younger than it actually is. Additionally, Belyaev and Glickman recognized that the accumulation of MnO2 on shark teeth did not begin as soon as they were deposited on the ocean bottom. Most of these teeth had been substantially degraded, with the roots completely disintegrated, before being encased in manganese.

With manganese eliminated as a viable indicator, dating the Challenger O. megalodon teeth must instead rely on coeval fossils. Belyaev and Glickman observed that O. megalodon often occurred in seafloor sediments with the ancestral white shark Carcharodon hastalis and false mako Parotodus benedeniiC. hastalis and P. benedenii are both shark species typical of the Mio-Pliocene marine fauna. I examined the other shark teeth collected by the Challenger, as figured in Murray and Renard (1891), in order to identify them according to modern taxonomy. I found specimens of both C. hastalis and P. benedenii, which dates the assemblage to the Mio-Pliocene and refutes a more recent age.

Even after the debunking of Tschernezky (1959), Roux and Geistdoerfer (1988) still used MnO2 to date O. megalodon teeth from off the coast of Madagascar. They estimated ages between 15,000 and 60,000 years old. However, since they also documented the presence of Parotodus, this “recent” occurrence can be dismissed as well. With this inaccurate approach having been disproven for nearly half a century, it is time to lay the contentions of Pleistocene-Holocene O. megalodon to rest. Cryptozoologists either have to accept that O. megalodon is extinct or continue to ignore the scientific evidence. The latter would entail hypothesizing that other Mio-Pliocene sharks also survive undetected.

Notes

1This appears to be a typographical error, as the correct calculation is 24,266.67.

Addendum (8/12/2022)

Destin Bogart of E.D.G.E. (who I collaborated with previously) has made an excellent YouTube video based on this post.

References

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