An international team of scientists has discovered an enormous whale graveyard stretching roughly 1,200 kilometres along the floor of the southeastern Indian Ocean, containing fossils dating back more than five million years. The site, described in a new paper published in the journal Nature, lies within the Diamantina Zone — a deep underwater fracture region formed when Australia broke away from Antarctica — at depths of between 4,200 and 7,000 metres, making it one of the deepest known whale-fall ecosystems ever found.

The discovery was made in February 2023, when researchers led by Xiaotong Peng of the Chinese Academy of Sciences descended to the seafloor aboard a submersible called the Fendouzhe. Following the initial find, the team conducted 32 further dives over the course of a month, identifying 476 whale fossils and five active whale falls — sites where carcasses continue to decompose on the ocean floor — spread across nearly 485 locations. Among the remains was a fossilised skull of Pterocetus benguelae, a now-extinct beaked whale dated to approximately 5.3 million years ago, as well as a five-metre-long Antarctic minke whale carcass, the largest single discovery at the site. The team also identified a previously unknown species, which they named Pterocetus diamantinae after the site itself.

The researchers believe the site's distinctive V-shaped topography plays a key role in its formation: ocean currents effectively funnel whale carcasses into the trench, where they sink to the bottom. The presence of decomposing remains then attracts rich communities of deep-sea life — sea cucumbers, mussels, tube worms, brittle stars, jellyfish and bone-boring worms among them — which in turn draw other predators, including more whales, creating a self-reinforcing cycle of biological activity. Many of the species found living on the carcasses may be entirely new to science.

"Discovering a necropolis of this scale was completely unexpected," Peng said. "The size of distribution, the depth and the age range were far beyond anything we had imagined." Palaeontologist Stephen J. Godfrey of the Calvert Marine Museum in Maryland, USA, described the paper as "a trailer for the first in a series of epic movies," adding that the site is likely to yield many more significant finds in the years ahead.

The discovery matters well beyond its sheer scale. The five-million-year-old fossils open a rare evolutionary window into the history of beaked whales from the Pliocene epoch to the present day, a period about which relatively little is known. More broadly, scientists say the find is a striking reminder of how much of the deep ocean remains unexplored — and how much may be waiting to be found when researchers look more closely.