Researchers have catalogued 381 previously-unknown species during a two-year study in the Amazon region.

The report by the World Wildlife Fund (WWF) conservation body and Brazil's Mamiraua Institute for Sustainable Development said researchers found a new species every two days during the survey.  These include a pink river dolphin with a population of around 1,000 individuals; and the fire-tailed titi-monkey, so named for its long, bright orange tail.

World Wildlife Fund

Most of the previously unknown species are plants, followed by fish, amphibians, mammals, reptiles, and a bird.

Unfortunately, all are located in areas at risk from development such as farming and logging, the authors warn.

"All the species that were discovered, all 381, are in areas where humankind is destroying the Amazon," said Ricardo Mello, coordinator of the WWF Brazil Amazon program.  "This is very important to us, because it links the fact that our economic activities are causing species to go extinct before we even know about them," he said, urging Brazilian authorities to protect the Amazon from destructive development.