Shark graveyard found deep in Indian Ocean

Australian scientists have uncovered what's being described as a "shark graveyard" during a research mission to the depths of the Indian Ocean.

A cluster of 750 fossilised teeth were found on the ocean floor more than five kilometres below the surface of the remote Cocos (Keeling) Islands Marine Park.

The teeth came from a range of species, including one that appears to have been more than 12 metres long and was likely an ancestor of the giant megalodon shark.

Curator of fish at the Western Australian Museum, Glenn Moore, said it was an incredible discovery.

"This shark evolved into the megalodon, which was the largest of all sharks but died out about 3.5 million years ago," he said on Wednesday.

"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." 

The discovery was made by scientists aboard the CSIRO research vessel Investigator.

During a more recent expedition to the Gascoyne Marine Park off Western Australia, the team made another landmark find of a new shark species.

CSIRO shark expert Will White said early in the voyage, they collected a "striking, small, stripey hornshark".

Hornsharks include the well-known Port Jackson shark and spend most of their day in shallow waters camouflaged among rocks and seaweed.

The new species was discovered at a depth of 150 metres, raising questions about this unusual behaviour.

"The specimen we collected will be incredibly important to science because we'll use it to describe the species," Dr White said.

A range of technologies were used to study the marine life and seabed habitats, including underwater towed and remote cameras, that on several occasions became a target for shark bites themselves.

Chief scientist on the current voyage, the CSIRO's John Keesing, said biodiversity surveys were continuing to turn up discoveries that take researchers by complete surprise.

"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 with the opportunity to learn more about marine ecosystems, as well as species range, abundance and behaviour."