This has been in a few different sources, including Australia’s ABC News, but the crew of a scientific submersible celebrated discovering an active “whalefall” in the Indian Ocean west of Perth — because once one of those massive corpses hits the bottom, it creates an ecosystem unto itself, feeding hundreds of different kinds of life forms. Then the submersible discovered another… and another… and some older ones… and some really older ones…. By the end of its run, they’d found five actively decomposing whales and 476 whale fossils, including a previously unknown extinct species dating back 5 million years:
Together, these traits make up the deepest and largest collection of whale fossils and falls found to date in the ocean.
“These findings reshape our understanding of the limits and biogeography of whale-fall ecosystems and establish some deep-sea floors as a fossil archive for tracing cetacean evolution over geological time,” study author and marine biodiversity researcher Xikun Song said.
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The whale graveyard was found during an expedition by the Chinese research vessel Tan Suo Yi Hao in March, 2023.
RV Tan Suo Yi Hao is often used for the Global Trench Exploration and Diving Program, a collaborative endeavour between China’s Institute of Deep Sea Science and Engineering (IDSSE) and several countries, including New Zealand.
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A human-piloted submersible vehicle, Fendouzhe, capable of reaching depths of 11,000m, was used during the expedition to explore the zone.
These depths ranged from 4,200m to 7,002m, with the first fossils found in a geological feature called Dordrecht Deep.
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Among the fossils was a skull fragment from an unknown species, which the new study named Pterocetus diamantinae.
Study author and palaeontologist Giovanni Bianucci, from the University of Pisa, said there was enough anatomical difference to distinguish the fossil from other species.
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But [study author Dr. Xikun] Song said the high concentration of beaked-whale species among the fossils could also be behaviour-related.
“Deep-diving beaked whales exceeding 3,000m may reach physiological limits, increasing the risk of fatal exhaustion or decompression sickness,” Dr Song said.
The V-shaped topography of the Diamantina Zone may also have helped funnel carcasses to the sea floor.
[Institute of Deep Sea Science and Engineering geologist Dr. Peng] Zhou said the preservation of the fossils for so long could come down to a combination of factors.
The first reason was that the fossils were mostly beaked whale rostra (noses), which were hyper-dense and mineral-rich, making them resistant to degradation.
“Second, the sedimentation rate here is extremely low … third, over time, ferromanganese oxide coatings form a protective crust on the bones,” Dr Zhou said.
“[And] fourth, the deep-sea environment is cold and stable, so physical and chemical weathering are minimal.”
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You can see video of submarines coasting over the whale necropolis here, on Nature Video.