Five new monkey species have just been added to the animal record books, according to a new study.

The primate additions — all saki monkeys from South America — mean that there are now 16 saki monkeys known to science. The monkeys are described in the study, which is published in the journal Neotropical Primates.

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All of the monkeys are beneficial to the environment, helping to disperse seeds in their tropical rain forest habitats.

“I began to suspect there might be more species of saki monkeys when I was doing field research in Ecuador,” Laura Marsh, director and co-founder of the Global Conservation Institute, said in a press release. “The more I saw, the more I realized that scientists had been confused in their evaluation of the diversity of sakis for over two centuries.”

The discoveries mark a recent trend of researchers analyzing data on certain animals, only to find that the look-alike individuals represent different species. In this case, the monkeys were thought to be subspecies or just variants of the known different types of sakis.

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The five new species are found in Brazil, Peru, and Bolivia. Their ranges extend throughout the Amazon Basin and the Guiana Shield. The monkeys are elusive, and for good reason: humans and other predators like to eat them. In other words, we’ve been killing animals not even knowing what they really were.

“This revision of the genus shows clearly how little we still know about the diversity of the natural world that surrounds us and upon which we ourselves depend so much,” said Russell Mittermeier, president of Conservation International and for whom one of the new species, Pithecia mittermeieri, was named.

The other new saki monkeys were named after other prominent primatologists and animal conservationists, such as Alcides Pissinatti and José de Souza e Silva-Júnior. One of the monkeys was also named after Isabel Gramesón Godin, considered “the first woman of the Amazon.” She lived in Colonial Peru (now Ecuador) in the 18th century and was the lone survivor of a grueling, 42-person, 3,000-mile expedition from her city in the Andes, all the way across the Amazon basin to French Guiana.

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Yet another primate expert who was honored with a namesake monkey, Anthony Reynolds of Conservation International, said, “In the 1980s, people believed that there were about 180 species of primates worldwide. Thanks to the dedication and skill of researchers such as Laura Marsh, today we have a clearer understanding of the diversity of the mammalian Order that gave rise to our own — 496 species, and counting.”

“Besides being vital for their conservation and survival, the revised scientific description of these sakis is a major step in our understanding of primate diversity in Amazonia and worldwide.”

Image: Pithecia pithecia, one of the five newly described saki monkeys. Credit: Conservation International/photo by Russell A. Mittermeier