Rats as big as cats, fanged frogs and grunting fish - they sound like something from a horror movie.
But, incredibly, there is a 'lost world' on a distant island where these nightmarish creatures really exist.
A team of scientists discovered the bizarre animals - and dozens of others - at a remote volcano in Papua New Guinea.
New species: Wildlife cameraman Gordon Buchanan with the Bosavi Woolly Rat
No fear: The rat is not afraid of humans, which could make it vulnerable
In the kilometre-deep crater of Mount Bosavi, they found a habitat teeming with life which has evolved in isolation since the volcano last erupted 200,000 years ago.
Among the new species was the the Bosavi Woolly Rat.
One of the biggest rats in the world, it measures just over 32 inches from nose to tail and weighs 3lb.
The silvery grey mammal has dense fur and its teeth suggest it has a largely vegetarian diet and probably builds nests in tree hollows or underground.
Surprising find: A new species of frog found near base camp. When scared it puffs up its body.
The Bosavi Woolly was discovered by a team from the BBC's natural history unit as they searched for new wildlife while filming the series Lost Land Of The Volcano.
During the trip to a little-known part of the rain forest, the team also found about 40 other new species, which are at various stages of verification.
This included a marsupial called the Bosavi Silky Cuscus, a camouflaged gecko, a fanged frog and a fish called the Henamo Grunter, which makes a grunting sound from its swim bladder.
New species: A frog named, Litoria sauroni, discovered on the trip
Picture shows: A bizarre jungle spider camouflaged as lichen
Researchers also found an extremely hairy caterpillar which is now awaiting cataloguing in Oxford, where the team will give names to their finds.
It is estimated that along with the giant rat and cuscus the expedition found about 16 species of frogs, one species of gecko, at least three species of fish, at least 20 of insects and spiders and possibly one new species of bat.
The expedition was led by climber and naturalist Steve Backshall-wildlife cameraman Gordon Buchanan and head scientist Dr George McGavin.
Mr Buchanan and Smithsonian biologist Dr Kristofer Helgen were first on the scene when the rat was found by a tracker from the local Kasua tribe. Dr Helgen said:
'This is one of the world's largest rats. It is a true rat, related to the same kind you find in the city sewers, but a heck of a lot bigger.
'I had a cat and it was about the same size of this rat. This rat was incredibly tame.
Picture shows: A bizarre hairy caterpillar found in the rainforest
Amazing: The king bird of paradise, and a buff faced pygmy parrot, found by bird expert Jack Dumbacher
'It just sat next to me nibbling on a piece of leaf. It won't have seen a human being before. The crater of Mount Bosavi really is the lost world.'
Papua New Guinea is famous for the number and diversity of rodents that live there, with more than 57 species from the Murid family of rats and mice on the island.
Further evidence of the rich wildlife of the tropical location came with the discovery of the Bosavi Silky Cuscus. This animal, which resembles a small bear, is a marsupial that lives up in trees, feeding on fruits and leaves.
Weighing in at some 4.5lb, it has thick silky fur adapted for the mountain environment in which it lives. Dr Helgen has identified it as a new subspecies in the group of strange marsupials known as cuscuses.
An iridescent Beetle found in the New Guinea rainforest
New species: A beautiful fruit dove discovered during the BBC expedition
He said: 'Long ago it was isolated on this volcano and has become something unique to Bosavi.'
The habitat in the area is currently regarded as pristine, but less than 20 miles to the south of Mount Bosavi extensive logging operations are happening.
The mountain acts like an island in the vast sea of jungle, trapping different species on it.
The expedition base camp was in the foothills east of Mount Bosavi with smaller teams going out to remote locations.
Lost Land Of The Volcano starts on BBC1 tomorrow at 9pm.