A shark graveyard containing fossilised teeth from an ancient ancestor of the massive but mysterious megalodon has been discovered by scientists exploring the deep ocean.
The team from the CSIRO research vessel, Investigator, have also collected a specimen from a new species of shark.
The extraordinary discoveries came during biodiversity surveys around the Cocos (Keeling) Islands in the Indian Ocean and the Gascoyne marine park off Western Australia.
Scientists were conducting a final trawl survey at a depth of 5400m when they spotted the graveyard, bringing up more than 750 fossilised shark teeth.
The megalodon ancestor tooth. Picture: CSIRO/Yi-Kai Tea
WA Museum curator of fishes Glenn Moore, who was on the voyage, said the shark teeth included a mix of modern and ancient sharks.
“The teeth look to come from modern sharks, such as mako and white sharks, but also from ancient sharks including the immediate ancestor of the giant megalodon shark,” Dr Moore said.
“This shark evolved into the megalodon, which was the largest of all sharks but died out about 3.5 million years ago.”
The megalodon is considered one of most powerful predators ever to have lived, but little is known for certain about the species — even its appearance and maximum size.
Scientists believe the teeth collected were likely from its closest relative, which reached more than 12m in length.
“It’s incredible to think we’ve collected all these teeth in a net from the sea floor some four to five kilometres below the ocean surface,” Dr Moore said.
Shark teeth collected near the Cocos (Keeling) Islands. Picture: CSIRO/Yi-Kai Tea
Australian National Fish Collection shark expert Will White said an exciting find from the underway voyage was the collection of a specimen of a new species of shark.
“Early in the voyage, we collected a striking small, stripey hornshark,” Dr White said.
“This species is unique to Australia, but it hasn’t yet been described and named.
“The specimen we collected will be incredibly important to science because we’ll use it to describe the species.”
Hornsharks are generally slow-moving species found in shallow waters, but this new species lives in water more than 150m deep and nothing is known about its behaviour.
Chief scientist on the underway voyage John Keesing said the discovery of new species was common on biodiversity surveys.
“It’s been estimated that around a third of the species collected on recent biodiversity survey voyages on RV Investigator may be new to science,” Dr Keesing said.
“The discoveries we make aren’t just limited to new species. These voyages give us the opportunity to learn more about marine ecosystems, as well as species range, abundance and behaviour.”
RV Investigator will continue surveying the Gascoyne marine park and the nearby Carnarvon Canyon marine park until mid-December.