A recent survey of Brazil's Caparao National Park turned up a rare discovery -- a new group of northern muriqui, one the planet's most threatened primate species.

The muriqui, sometimes called the woolly spider monkey, is the New World's largest primate. In the 1980s, biologists separated the primates into two species, the northern muriqui, Brachyteles hypoxanthus, and the southern muriqui, Brachyteles arachnoides.

The latest discovery is good news for conservationists who have fought hard to protect the monkeys. Facing the pressures of hunting and habitat destruction, numbers of both species have declined over the last 50 years.

The northern muriqui are endemic to eastern Brazil's Atlantic Forest. They're now relegated to a handful of protected forests. Each fragment of habitat hosts around 100 monkeys, making up a total wild population of less than 1,000.

Caparao National Park has been identified as a potential hotspot of muriqui conservation, but until now, researchers didn't know much about the subpopulation living here. It turns out the previously unrecognized group is rather significant.

"It was a great surprise, because the group was found in an area of the park where the species had never been recorded before," Mariane Kaizer, a researcher with the Conservation Leadership Programme who led the recent survey, said in a press release.

"The group is big and healthy!" Kaizer said. "We had the opportunity to count at least 50 individuals including seven juveniles and five infants. It is really fantastic news for northern muriqui conservation."

Kaizer and her colleagues say they will continue field research efforts with hopes of better understanding the distribution, density and status of the muriqui and other threatened species.

The park -- which encompasses Pico da Bandeira, Brazil's highest mountain -- is home to variety of monkeys, including the endangered huffy-headed marmoset, a tiny, squirrel-like monkey, as well as the near threatened black-fronted titi and black-horned capuchin.

New data on these species and others will inform and improve conservation management plans.