okapi (ōkăpˈē) [key], nocturnal ruminant mammal, Okapia johnstoni, of the giraffe family. It inhabits the almost sunless rain forests of the upper Congo and feeds on leaves. Its shape is reminiscent of a giraffe's, but it is smaller, with a much shorter neck. It is deep reddish brown with black and white zebra-striped legs. Its head is giraffelike and in the male bears blunt skin-covered horns. The okapi was unknown to zoologists until the beginning of the 20th cent. It is classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Artiodactyla, family Giraffidae.