Scientists discover 1,200 km whale graveyard in Indian Ocean, with fossils dating back 5.3 million years

The discovery

An international team of researchers from China, Italy, and New Zealand has discovered the largest, deepest, and oldest whale graveyard ever found. The site, located in the Diamantina Fracture Zone in the southeastern Indian Ocean, extends for approximately 1,200 kilometres at depths ranging from 4,200 to 7,000 metres. The findings were published in the journal Nature.

During 32 submersible dives conducted in 2023 using the Chinese deep-sea vehicle Fendouzhe, the team identified 485 fossil sites and five active whale falls—carcasses that are still being actively colonised and consumed by other organisms. The density of remains reaches 759.5 individuals per square kilometre, suggesting the area could contain over 10 million whale carcasses.

“Discovering a necropolis of this magnitude was completely unexpected. The extent of the area, the depth, and the age of the remains far exceed anything we had imagined.”

Ancient remains and new species

The oldest fossils recovered date back 5.3 million years. Among the finds was a fossilised skull of Pterocetus benguelae, a beaked whale species, and a five-metre Antarctic minke whale carcass, the largest specimen found. The team also identified a previously unknown extinct species, which they named Pterocetus diamantinae after the discovery site.

Most of the fossils belong to beaked whales (ziphiids), a group of toothed cetaceans known for their extreme deep-diving behaviour. Researchers speculate that the V-shaped troughs of the Diamantina Fracture Zone may have funnelled dead animals into the area, where currents carried them before they sank.

“These are 'laboratories of evolution': uniquely adapted life forms evolve here that are found nowhere else.”

Deep-sea ecosystems

When a dead whale sinks and settles on the ocean floor, it can give rise to a rich and complex ecosystem that supports a wide range of organisms. On the remains, researchers found diverse species including jellyfish, brittle stars, bone-eating worms (Osedax), and molluscs living in symbiosis with bacteria. At such depths, the seafloor is typically desert-like, and whale carcasses form isolated, self-sufficient islands of life that can provide nourishment for hundreds of years.

“The imposing size of whales and the particular chemical composition of their bones are fundamental to the formation of these unique underwater settlements. At the same time, the very nature of the ocean abyss makes these sites exceptionally difficult for scientists to locate.”

Scientific significance

The discovery surpasses the previous depth record for a whale fall, which was in the southwestern Atlantic at approximately 4,200 metres. The excellent preservation of the bones is attributed to their high density, which resisted worm activity, and the protection afforded by the great depth, where there is less chance of being buried by sediment. A mineral coating also formed on the bone surfaces, acting as a protective film.

“The discovery of this vast fossil cemetery by Peng and colleagues is a truly unique find. Although access to the site is limited, it likely holds many more fascinating discoveries and will undoubtedly inspire future submersible dives in similar environments.”

The research team believes the site will be studied for years to come, with many of the organisms found likely belonging to species or subspecies never before documented.