An adorable monkey that purrs like a cat is just one of many new species recently discovered in a remote section of the Amazon rainforest.

A group of scientists, with the help of World Wildlife Fund, have spent more than four years in what's considered an under-explored rainforest, discovering as many as 441 new species of plants and animals during their studies.

The study yielded discoveries of 258 new species of plants, 84 fish, 22 reptiles, and 18 birds. Have a look at a few of the species discovered below, or click here to peruse the complete list.

Photos and captions from WWF.

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Callicebus caquetensis – Colombia | This new species, Callicebus caquetensis, is one of about 20 species of titi monkey, which all live in the Amazon basin. The babies have an endearing trait, “When they feel very content they purr towards each other,” explained scientist Thomas Defler. Photo credit: Thomas Defler.



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Allobates amissibilis - Guyana | This amphibian is already believed to be highly endangered. In fact, its Latin name, Allobates amissibilis, meaning “that may be lost,” alludes to this, as the area where it thrives could soon be opened to tourism. Photo credit: Philippe Kok.



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Passiflora longifilamentosa –Brazil | A new species of passion flower was discovered in the rain forests of the Brazilian state of Para in 2013. Together with vivid purple petals, the new species displays fantastic and quirky 'noodles' or 'spaghetti' (corona filaments) that burst out of the flower's centre. Photo credit: Joao Batista Fernandes da Silva.

Tometes camunani – Brazil | This new species of piranha, Tometes camunani, can span 20 inches wide and weigh up to 9 pounds, and is strictly herbivorous. The freshwater fish inhabits rocky rapids associated with seedlings of plants that grow among the rocks, its main source of food. Photo credit: Tomasso Giarrizzo.

Chironius challenger – Guyana and Venezuela | Found in the mountains of Guyana, at elevation of 4,922 ft., this brightly-colored snake species was named Chironius challenger after Arthur C. Doyle's fictional character Professor George Edward Challenger in the novel The Lost World. Photo credit: Philippe Kok.



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