A 5.3-million-year-old deep-sea whale necropolis in the Diamantina Zone

Key Points:

• Researchers discovered extensive whale-fall communities and fossils in the Diamantina Fracture Zone of the Indian Ocean, at depths up to 7,079 meters, establishing one of the deepest known whale-fall ecosystems and expanding the depth range by over 2,500 meters.
• The study documented 485 whale-fossil sites and active whale falls along a 1,200 km seafloor stretch, revealing diverse macrofauna dominated by annelids, crustaceans, molluscs, and specialized species such as bone-eating worms and chemosymbiotic bivalves, many potentially new to science.
• Fossil analysis identified five beaked-whale species and one baleen-whale species, including extinct genera Pterocetus and Izikoziphius, providing a rare deep-sea fossil megasite that offers insights into evolutionary history and population dynamics of deep-diving cetaceans from the Pliocene to present.
• The accumulation of whale remains is attributed to natural mortality, deep-diving behavior limitations, and the unique V-shaped topography of the Diamantina Zone, which funnels carcasses to the seafloor, while ultra-low sedimentation rates contribute to long-term preservation.
• Findings suggest the Diamantina Zone whale-fall communities act as evolutionary hotspots and biogeographic corridors for deep-sea chemosynthetic fauna, enhancing understanding of species richness, connectivity, and adaptive radiation in extreme ocean environments.