The creature, officially named Paludirex vincenti, measured more than 16 feet (five meters) long and dominated waterways in southeastern Queensland, according to a press release from the University of Queensland (UQ) published Monday.
It lived between 5.33 and 2.58 million years ago, researcher Jorgo Ristevski, a PhD candidate at UQ's School of Biological Sciences, told PeerJ, the journal which published the research.
Researchers identified the giant crocodile from fossils dug up in the 1980s near a town named Chinchilla.
The species is named after Geoff Vincent, who found a fossilized skull of the prehistoric animal. "Paludirex" means swamp king in Latin and "vincenti" honors Vincent, according to Ristevski,
"The 'swamp king' was one intimidating croc," said Ristevski in the press release. "Its fossilized skull measures around 65 centimeters, so we estimate Paludirex vincenti was at least five meters long."
The largest living crocodile, the Indo-Pacific crocodile -- Crocodylus porosus -- grows to about the same size, he added.
"But Paludirex had a broader, more heavy-set skull so it would've resembled an Indo-Pacific crocodile on steroids," said Ristevski.