Wellington: Scientists have linked a fossilized tooth - found in 1994 Gippsland, Victoria - to the biggest and oldest aquatic reptile to have called Australia their home.
The tooth is the first proof that the carnivore, known as a pliosaurid, swam in southern Australia`s waterways, Stuff.co.nz reported.
At five metres in length, the ancient reptile was nearly 3 m longer than the previous record holder, a plesiosaur, which roamed Australia`s rivers during the Cretaceous period 120 million years ago.
Museum Victoria palaeontologist Erich Fitzgerald said that the two had not been found together in waterways anywhere in the world before.
Both reptiles were confined to water, as they were unable to walk on land due to their large flippers.
The reptiles` range would have been limited only by the waterways, some of which stretched for up to 2000km.
The larger pliosaurids ate fish and small terrestrial animals and occasionally ate small dinosaurs that let their guard down while crossing a river or venturing to the water for a drink.
The fossil is only part of the tooth - a 3cm-long tip from an entire tooth that was probably double that in length.
The tooth was found in coastal Gippsland, but 120 million years ago the area would have been more than 1500km inland.
The findings have been published in Alcheringa: An Australasian Journal of Palaeontology by Fitzgerald and colleagues Thomas Rich, Patricia Vickers-Rich and Roger Benson.