During an expedition to Indonesia’s remote eastern province of Papua, scientists from Conservational International discovered two mammals believed to be new to science.

Together with researchers from the Indonesian Institute of Sciences, they documented the two mammals, a Mallomysgiant rat and a Cercartetus pygmy possum, during an expedition to Papua’s Foja Mountains in June.

The giant rat weighting 1.4 kilograms is about five times the size of a typical city rat, Dr. Kristofer Helgen, a scientist with the Smithsonian Institution in Washington said, according to The Press Association.

The pygmy possum was described as “one of the world’s smallest marsupials.”

Scientists are currently studying the two species in more detail to ascertain whether they are genuinely new species and, if so, where exactly they fit.

The team first visited the Foja Mountains in 2005. The region is believed to have never been touched by any modern human. Because of its isolation, scientists called it the “Lost World.” With 42 million hectares of tropical forests and some of the richest biodiversity in the world, Papua is considered the country’s last rainforest frontier. The region is however under threat because of increased cutting and clearing from palm oil plantations as well as rampant illegal logging.

Back in 2005, scientists discovered here dozens of new plants, birds, butterflies and frogs.

"It's comforting to know that there is a place on Earth so isolated that it remains the absolute realm of wild nature. We were pleased to see that this little piece of Eden remains as pristine and enchanting as it was when we first visited," said expedition leader Bruce Beehler, vice-president of the US-based wildlife group Conservational International.

A third expedition is planned  for next year, as scientists heard the calls of birds they could not identify and were convinced there were many more creatures yet to be discovered in the almost-forgotten world.