NEW YORK (AP) — Scientists have unearthed communities of marine life — including jellyfish, tubeworms and brittle stars — thriving on a millions-year-old whale graveyard.

These graveyards form when whale carcasses fall to the sea floor, becoming a sustaining snack for nearby critters. This one, located up to 23,000 feet (7 kilometers) below the surface of the southeastern Indian Ocean, spans the largest area and is so far the deepest and oldest found.

A whale's sheer size and the unique chemistry of its bones are the keys to forming these unique underwater neighborhoods, said Xikun Song, a biologist with the Chinese Academy of Sciences' Institute of Deep-sea Science and Engineering.

“At the same time, the very nature of the deep ocean makes these sites exceptionally difficult for scientists to locate,” Song, who was involved with the latest find, wrote in an email.

Researchers explored the remains during multiple deep-sea submersible trips in 2023, collecting samples and mapping the extent of the necropolis. They found five carcass sites and fossils, including skulls belonging to beaked and baleen whales. The oldest bones date back 5.3 million years.

Feeding and living on the carcasses were myriad creatures, large and small, including sea cucumbers, squat lobsters and saltwater clams. Many of them are likely species that have never been documented, according to findings published Wednesday in the journal Nature.

“The potential number of specimens is just astounding,” said paleontologist Stephen Godfrey with the Calvert Marine Museum in Maryland, who wasn't involved in the research.

Many factors likely conspired to preserve the bones for millions of years, according to the study authors. They’re dense enough to outlast attacks from bone-eating worms, and located deep enough in the ocean to avoid getting buried by dust and loose particles. The bones were also coated with a light layer of minerals from the surrounding seawater, which may have prevented them from degrading.

Why did so many whales die here? Maybe they were already living in the area and died of natural causes. A few could have perished from exhaustion or illness caused by deep-sea diving. The area's shape, akin to the letter V, could also have funneled the remains to their resting spot, the authors wrote.

Such discoveries are important because they clue scientists into the vibrant communities that find a way even in remote, hard-to-reach environments.

Studying the whale graveyards “is important for understanding how life can adapt to such extreme conditions, not only due to the lack of light and oxygen but also to the incredibly high pressure,” said study co-author and paleontologist Giovanni Bianucci with the University of Pisa in Italy in an email.