High in the forested canopy of Democratic Republic of Congo, an all-black monkey turned its back to a photographer’s camera. The partial image taken in 2008 revealed little more than the monkey’s dark coat and part of its tail. But it was enough to get Junior Amboko, a biological primatologist at Florida Atlantic University in Boca Raton, and other researchers wondering if the photo revealed a species unknown to science. Over the next several years, Amboko and his colleagues returned to the dense, closed-canopy forest, where the mystery monkey shared its range with seven other monkey species and bonobos. From 2018 to