Indian Ocean Whale Graveyard Spanning Five Million Years Unveiled

In a dramatic deep‑sea expedition, Chinese scientists and an international team discovered one of the world’s largest whale necropolises in the Diamantina Fracture Zone of the southeastern Indian Ocean. The site, extending roughly 1,200 km (745 mi) along a V‑shaped trench, contains over 480 fossilized whale skeletons deposited over the past five million years.

Using the HOV Fendouzhe submersible, the researchers carried out 32 dives in 2023, documenting 485 fossil whale sites and five modern whale falls. The depth of the trench, ranging from 4.5 km (3 mi) to about 7 km (4 mi) below sea level, made it an ideal funnel for carcasses to settle and remain exposed for scavengers.

Most of the fossils belong to the elusive beaked whales, a deep‑diving cetacean family rarely seen alive. In addition to ancient beaked whale remains, the team identified a 5.3 million‑year‑old skull of the extinct genus Pterocetus, and a new species, Pterocetus diamantinae, named after the discovery site.

Beyond the paleontological interest, the whale graveyard serves as a living laboratory for deep‑sea biology. The carcasses host vibrant “whale‑fall” ecosystems, where species such as jellyfish, brittle stars, bone‑boring worms, spiny sea cucumbers, and clams with chemosynthetic bacteria thrive. One modern cadaver supported up to 2,840 individual organisms on a single square meter, highlighting the enormous food resource a whale provides to deep‑sea communities.

Lead author Xiaotong Peng noted that the scale, age range, and depth of the site exceeded expectations. “We were astonished by the sheer number of whale remains; the distribution is far beyond anything previously recorded,” he said. The study estimates over 10 million whale carcasses at the site, with an associated 6.7 million tonnes of sequestered carbon locked in the bones.

Scientists believe the trench’s geometry acted like a natural filter, funneling whales that died during deep‑sea foraging or due to decompression into a narrow, sediment‑quiet area. The resulting accumulation created a pervasive resource that supports a unique assemblage of deep‑sea species, many of which may be new to science.

“This discovery not only sheds light on ancient whale migrations but also underscores the ecological significance of whale falls in deep ocean ecosystems,” said palaeontologist Stephen Godfrey. He emphasized that further submersible dives could reveal more sites, potentially across similar trenches near South Africa, the Iberian Peninsula, and the Kerguelen Islands.

With the Diamantina necropolis now documented, researchers will continue to study how whale falls contribute to evolution, biogeochemical cycles, and the structure of deep‑sea food webs. The findings also provide a unique record of Pliocene ocean conditions and cetacean dispersion patterns, enhancing our understanding of marine mammal history.