Australian researchers say they've found the remains of the largest rat ever known, weighing more than 13 pounds and about the size of a small dog.

Scientists from the Commonwealth Scientific and Industrial Research Organization found the bones of the species in a cave in East Timor, an island nation north of Australia, the Australia Broadcasting Corp. reported Monday.

The large rats survived until about 1,000 to 2.000 years ago, CSIRO scientists said.

They dominated the animal kingdom on East Timor about five million years ago, the research team said.

"It was rat land with at least 13 species of rodents on an island that isn't that big," archaeologist Dr Ken. Aplin said.

"So it's incredible diversity," he said.

A CSIRO team plans to investigate an area of swampy rainforest where 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," Aplin said.

"And if so we need to act quickly to conserve them."