okapi (ōkăp´ē), 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, hornlike ossicones that are made of ossified cartilage. 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.