JOIN USThe skeletal remains of the monster rat, which is believed to have an estimated body weight of about six kg, were found during cave excavations in East Timor.
The excavations carried out by a team from CISCO -- Australia's national body for scientific research -- also turned up 13 other species of rats, 11 of which are new to science, with eight of the rats estimated to have weighed more than 1 kg.
The researchers believe the giant rat survived upto until about 1,000 to 2,000 years ago. Today's heftiest rats weigh around 2 kg and live in rain forests in the Philippines and New Guinea.
Dr Ken Aplin, who led the excavation, said the latest findings indicate the rodents dominated the East Timorese animal kingdom about five million years ago.
"It was rat land with at least 13 species of rodents on an island that isn't that big," he was quoted as saying by the ABC News.
"So it's incredible diversity," he said, adding large-scale clearing of forest for agriculture probably caused the extinctions.
"This may have only been possible following the introduction of metal tools," Aplin said.
The team now plans to investigate an area of swampy rain forest where they believe some rare grass-eating rat species may still survive.
"I do hold out that hope that some of the smaller species and some of possibly one or two of the largest animals, these grass-eating specialists, might still survive," Dr Aplin said.
"And if so we need to act quickly to conserve them."The findings have appeared in the Bulletin of the American Museum of Natural History.