Museum Victoria palaeontologist Erich Fitzgerald said the find was internationally significant, as it represented the first evidence of such a gigantic sperm whale outside the Americas. Dr Erich Fitzgerald with the sperm whale tooth. Credit:Ben Healley, Museum Victoria Fossil enthusiast Murray Orr stumbled on the 30-centimetre-long tooth on Beaumaris beach in February 2016, a world-renowned fossil site dating back 66 million years. The area is considered a magnet for marine megafauna, with the fossil record preserving a variety of sea life that once inhabited the area. "When you find something that is special, you know it," Mr Orr said. However he wasn't immediately sure of what he had found - or of its scientific significance. At first, it was the round base of the tooth that caught his eye. Thinking it was a discarded drink can, he bent down to clear away some smaller rocks and pick it up.

Pulling the fossil upwards, free of the mud, he soon realised it was a lot longer than a drink can. Murray Orr with the fossil tooth on the day he found it. Credit:Murray Orr "As it was coming out I thought it might be an anti-aircraft shell, I thought 'here we go, I'm going to blow my arm off'...but then I noticed the curve and thought it looked like a whale tooth." A keen fossil fossicker with 45 years experience Mr Orr, 60, has donated the tooth to Museum Victoria, where it will prove a key asset to scientific research and education. Hailing from the Pliocene epoch, the fossilised tooth is estimated to be about five million years old - making it the youngest known fossil of the ancient whale-eating sperm whale.

Unlike present-day sperm whales which prey on squid and fish, the tooth of this sperm whale reveals it was a fearsome predator. Such insight adds to knowledge of the evolution of marine megafauna. "If we only had today's deep-diving, squid-sucking sperm whales to go on, we could not predict that just 5 million years ago there were giant predatory sperm whales with immense teeth that hunted other whales," Dr Fitzgerald said. Closely related to a species from Peru, Livyatan melvillei, the Beaumaris sperm whale had dental dimensions exceeding that of Tyrannosaurus rex. Intriguingly, Dr Fitzgerald said the tooth was incomplete - missing the tip of the crown and some of the base of the root. "It gets even more exciting though as this is the tooth of a whale which was not fully grown," Dr Fitzgerald said. "If the whale had lived longer it would have been bigger."