Chinese submersible finds 5.3-million-year-old whale graveyard 7 km deep in the Indian Ocean, the largest and oldest ever recorded
Scientists aboard China's Fendouzhe submersible have mapped a 1,200 km corridor of nearly 500 whale skeletons on the Indian Ocean floor, with some fossils dating back 5.3 million years and five active carcasses still feeding deep-sea ecosystems.
A necropolis in the abyss
During 32 dives in 2023, researchers from China, Italy and New Zealand explored the Diamantina fracture zone, a rift valley between Australia and Antarctica where the seafloor plunges past 7,000 metres. They identified 485 sites containing whale remains, including roughly 500 fossils and five modern carcasses in advanced decomposition. The oldest recovered skull was dated to approximately 5.26 million years, predating the emergence of Homo sapiens by a vast margin.
Discovering a necropolis of this scale was completely unexpected: the size of distribution, the depth and the age range were far beyond anything we had imagined.
The bones are spread along a northwest-southeast axis for 1,200 km, forming what the team calls a previously unrecognised "whale-fall community supercorridor." The largest single carcass was a five-metre Antarctic minke whale.
Life without sunlight
At depths where no sunlight penetrates, a dead whale becomes an oasis. Around the five active falls, scientists documented colonies of Osedax bone-eating worms, brittle stars, jellyfish, bivalve molluscs, sea cucumbers, squat lobsters and microbial mats that survive on chemical reactions rather than solar energy. Many of these organisms are believed to be species new to science.
The sheer size of a whale and the distinct chemistry of its bones are crucial to the creation of these deep-sea havens.
The discovery pushes the known depth limit for whale-fall ecosystems far beyond the previous record of 4,204 metres, set by a single carcass in the southwest Atlantic in 2016.
Why so many whales died here
Most of the fossils belong to beaked whales, an elusive group that hunts squid and fish at great depths. Researchers propose several explanations for the concentration: the zone may be a prime foraging area, and its V-shaped trench could funnel carcasses to the ocean floor. The beaked whales' deep-diving lifestyle, with maximum dives estimated beyond 3,000 metres, may also contribute to natural mortality in the region.
This discovery demonstrates that these extreme and unexplored environments are home to species and ecosystems still unknown to science, and that we are therefore still far from understanding the true biodiversity of our planet.
A fossil archive and carbon store
The bones' preservation owes much to their high density, which resisted bone-eating worms, and to a protective mineral coating formed from dissolved substances in the seawater. Their extreme depth also shielded them from burial by sediment. Extrapolating from the bone count, the scientists estimate more than 10 million carcasses could lie across the Diamantina Zone, representing roughly 6.7 million tonnes of sequestered carbon.
- Diamantina fracture zone forms as Australia and Antarctica separate.
- Oldest whale fossil in the graveyard dates from this period (Pterocetus benguelae).
- Chinese submersible Fendouzhe conducts 32 dives, discovering 485 fossil sites and five active whale falls.
- Findings published in Nature, revealing the largest, deepest and oldest whale graveyard on record.
New species and extinct whales
Among the remains, the team identified an extinct species named Pterocetus benguelae and a newly discovered species they called Pterocetus diamantinae, after the site. Paleontologist Stephen Godfrey, writing in Nature, compared the find to the first observation of hydrothermal vents teeming with life in 1977 and described the research as "a trailer for the first in a series of epic movies." The team expects many more discoveries as analysis of the collected samples continues.
