Scientists have discovered dozens of new species of animals and plants in a remote 'Lost World' in the dense forests of Papua New Guinea, an island north of Australia. Among them are 50 new types of spider, a striped gecko and three frogs - including one with a loud ringing call. The unique creatures, which have never been documented before, were found by a team of scientists with Conservation International, who made the discoveries during a four-week expedition to the country's unexplored Kaijende highlands and Hewa wilderness

A Litoria frog, which uses a loud ringing song to call for a mate, was one of the new species of frog found. During the survey more than 600 species were documented over a number of different taxonomic groups including amphibians, mammals, birds, reptiles, plants, and invertebrates. Of the discoveries made, a large number of species were found to be potentially new to science, and of these many are now being published and given scientific names

A jumping spider species new to science, Tabuina varirata was found on a conifer tree in a rainforest clearing. Wayne Maddison, a researcher at the University of British Columbia who contributed to the research, said three of the 50 new spider varieties discovered were particularly special. "They are strikingly distinctive evolutionary lineages that had been unknown before, with a group that is already very distinctive on the evolutionary tree of jumping spiders. Their key position on the evolutionary tree will help us understand how this unique group of jumping spider has evolved"

Scientists examining the newly discovered jumping spider Tabuina varirata. The expedition included researchers from Conservation International, the University of British Columbia in Canada, Montclair State University in New Jersey, and experts from the native Hewa tribe

Orthrus, a jumping spider species potentially new to science. New Guinea, an island north of Australia that is split between Papua New Guinea and Indonesia, has proven a rich hunting ground for biologists

A third new jumping spider species, Uroballus, found in the rainforest. Conservation International, based in Washington DC, America, says it has previously found more than 600 new species elsewhere on the island of New Guinea

The Cyrtodactylus bent-toed gecko is another species believed to be new to science

This Oreophryne is an as yet undescribed species of microhylid frog which has a sharp chirping call. Believed to be new to science, it was discovered in limestone hills in Papua New Guinea's highland wilderness

A large tree frog, Nyctimystes, with enormous eyes, was discovered by scientists next to a clear-running mountain river