NAIRPOBI, Kenya — The world’s newest-known monkey is a shy creature with bright-blue buttocks that lives quietly in the remote rain forests of central Africa, according to the American researchers who discovered a new monkey species. Cercopithecus Lomamiensis, locally called the lesula, is barefaced and has a long nose and an aquamarine backside. It is well-known to hunters in the Lomami forest basin in the Democratic Republic of the Congo, but researchers said the area has had little biological exploration and the species was unknown to those outside the region.