A time capsule at 3,000 m — megalodon teeth found in situ for the first time

A giant shark from 3.5 million years ago

Traces of a massive shark that went extinct 3.5 million years ago were found resting on the seafloor at 3,000 metres.

Otodus megalodon. Estimated length: over 15 metres. Shark skeletons are cartilage and rarely fossilise, but teeth are different. Sharks shed teeth constantly, and they accumulate on the ocean floor.

First ever in-situ deep-sea discovery

In 2022, ROV Hercules aboard E/V Nautilus recovered a fossilised megalodon tooth near the Johnston Unit of the Pacific Remote Islands Marine National Monument. Depth: over 3,000 metres. It was the first time a megalodon tooth had been found and documented in situ in the deep sea.

Previously, deep-sea shark tooth fossils were collected by net-dragging, which meant no precise location data. ROV discovery solves that problem.

Ferromanganese records time

Teeth that sit on the deep seafloor for long periods become coated in ferromanganese minerals. The coating grows at roughly 2.5 mm per million years. Measuring its thickness gives an estimate of how long the tooth has been there.

During the 2025 NA176 expedition, fossilised shark teeth were also found at depths exceeding 5,100 metres in Cook Islands waters.

What teeth on the seafloor can tell us

Megalodon teeth have serrated edges similar to great white sharks, suggesting comparable predation behaviour. Clues to the extinct giant's ecology may still be lying on the deep-sea floor in untold numbers.

For more deep-sea discoveries, see 'CCZ deep sea: 24 new species including a new superfamily.'

A note from the author: The fact that ferromanganese thickness can date a tooth amazed me. 2.5 mm per million years. Time literally layers itself onto the surface.

The thought that these teeth lay undiscovered in the deep-sea dark for 3.5 million years is quietly astonishing.