The discovery of a fossilised tooth in-situ in the deep, mid-ocean sheds light on megalodon’s migratory behaviour
A new paper published in the online journal Historical Biology has described the first reported case of a fossilised megalodon tooth found in-situ on the deep sea floor, where it has lain undisturbed for millions of years.
The discovery was made at a depth of 3090m, during an ROV dive in the Central Pacific Ocean, part of NOAA’s E/V Nautilus program of deep-sea exploration. The tooth was filmed as it lay embedded in the sand of a narrow ridge that forms part of a mid-ocean seamount approximately 350 km southeast of Johnston Atoll.
Famous for inaccurate speculation over its continued existence, the fossilised teeth of Otodus megalodon – which died out between 2.5-3.5 million years ago – have been quite commonly found in marine sediments dating to the late Miocene and early Pliocene eras, when megalodon was one of the largest and most populous sharks in the world’s oceans.
Estimated to reach a maximum of around 20m in length, megalodon is one of the largest marine predators that has ever existed, and, consequently, its massive teeth are somewhat easier to find than those of other, smaller sharks. Most of the fossilised teeth that have been found were collected from shallow-water sediments close to the shoreline, leading to the conclusion that O. megalodon was a largely coastal species.
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Tracing back through previous studies, however, the new report’s authors found that megalodon teeth had been previously recorded in offshore locations at depths between 350 to 5570 metres, indicating that megalodon was likely to migrate vast distances across oceans, a similar behaviour to large predatory sharks of the modern era.
The location on the ridge where the tooth was found is of a type often targeted by Nautilus during its ROV dives, as the topography creates conditions where currents are strong enough to prevent sediment from settling but not strong enough to displace larger objects. According to the new study, the well-preserved serration of the tooth’s cutting edges indicated it had not been transported any distance, and had not been covered by sediment, despite being measured – at a minimum – of 3.5 million years old.
The tooth measured 6.8cm in length, implying it was from a juvenile or young adult of the species, as megalodon teeth measuring more than 15cm in length have previously been found. The discovery adds a little more to the history of the world’s most notorious prehistoric shark, which up until recently had been presumed to be a giant ancestor of the great white shark.
A 2012 study, however, found that the shape of the great white’s teeth was more closely related to that of a different species of shark thought to be the prehistoric ancestor of the modern mako shark, implying Otodus megalodon was the last in a long line of extinct ‘megatoothed’ sharks.
The full paper, ‘First in situ documentation of a fossil tooth of the megatooth shark Otodus (Megaselachus) megalodon from the deep sea in the Pacific Ocean’ by Jürgen Pollerspöck et al is published in Historical Biology
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