by A graveyard filled with thousands of shark teeth lies nearly 3.5 miles (5,400 kilometers) below the surface of the Indian Ocean.
Researchers made the shocking discovery in October during a month-long expedition along the southern tip of Indonesia in Researcher RV (opens in new tab), a 308-foot (94 m) research vessel operated by the Commonwealth Scientific and Industrial Research Organization (CSIRO), Australia’s national science agency. On the last day of the trip, and after 26 previous attempts, the researchers sank a trawl net into deep water hoping to catch fish as part of an ongoing biodiversity survey. Instead, they pulled out a net with hundreds of shark teeth, according to a statement (opens in new tab).
“It was our last sample of the trip before returning to Australia.” Dianne Bray (opens in new tab), senior director of collections at the Museums Victoria Research Institute, told Live Science. “At first I was a bit disappointed when we lifted the net because it was full of mud and I knew there wouldn’t be many sample fish. mud.”
But as researchers sifted through the mud-created material, they realized the capture wasn’t just a colossal mud pie.
“We turned the contents over on the deck of the boat and as we went through everything, we found shark tooth after shark tooth,” Bray said. “We were finding teeth from [modern] even [great] white sharks, but also fossilized teeth from ancient sharks such as the direct ancestor of the giant megalodon shark.”
Related: Amazing Sharks: The World’s Biggest, Smallest, and Weirdest Sharks
In all, the researchers collected more than 750 teeth that ranged in size from 0.39 inches (1 centimeter) to a single tooth from Megalodon’s ancestor measuring 4 inches (10 centimeters).
The researchers noticed deposits of black manganese nodules growing on many of the teeth, which were the result of the teeth sitting on the ocean floor for such a long time. Otherwise, the teeth were all in good condition.
“It’s pretty remarkable,” Bray said. “The teeth were not worn, buzzed or cracked. Bacteria it consumed all the organic matter from the teeth and the roots were gone, but otherwise the enamel remained.’
Researchers aren’t entirely sure why so many teeth piled up in that part of the ocean, but they don’t think hundreds of sharks died there, Bray said. Unlike humans, who are born with a set of baby teeth and replace them with a set of adult teeth during their lifetime, sharks have an endless supply of teeth that are replaced “like conveyor belt,” Gareth J. Fraser, a lecturer at Evolutionary Developmental Biology at the University of Sheffield in the UK, wrote in The conversation (opens in new tab).
The area where the teeth were found likely housed an ancient shark community.
“The teeth were found in an abyssal plain and not out in the open ocean,” Bray said. “This area was part of an ancient reef covered in seamounts, and we believe a community of sharks swam around this area a long time ago.”
As they swam, their used teeth probably fell out.
Bray said the shark’s teeth barely “scratched the surface” of what was buried there.
