A tooth that belonged to an ancient giant shark has been stolen from a World Heritage Site in Australia, authorities have said.

The 8cm  tooth went missing from an undisclosed location in a remote national park in Western Australia.

The fossil came from the Megalodon species, a giant predator that is believed to have died out about 2.6 million years ago.

Authorities suspect the tooth was deliberately targeted by thieves.

It was one of two Megalodon teeth located in the Unesco World Heritage-listed Ningaloo Coast, according to Western Australia's Department of Environment and Conservation.

"The worst part is they took the better specimen, which was not so well known," said spokesman Arvid Hogstrom.

"Our staff had actually physically covered it up with natural features to make sure it was hidden."

Mr Hogstrom said the stolen tooth had been in a semi-secret location and attached to a rock. Unlike the other tooth, it was not visited by tourists.

Mr Hogstrom said only a small group of locals and others knew of its location. He suspected that a person may have "unwittingly told someone who decided to do the wrong thing".

The fossil was most likely removed with a hammer or a chisel, he said - a breach of vandalism and conservation laws.

He said the monetary value of tooth was not known but it "would not be very high".

The fossil had been well preserved from ancient times.

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