Although you might not expect it, the okapi's closest living relative is the modern-day giraffe, Giraffa camelopardalis. While they share many similar features with each other, one did not evolve from the other. Much of their evolutionary history lies in the Miocene period of Africa, when the first of the Giraffidae family diverged from the other ruminants which lived during that time period roughly 25 million years ago. It's suggested that it wasn't until the late Miocene period that the genus Samotherium actually split into the genus Okapia roughly 18 million years ago. Although Samotherium was already considered a short-necked giraffe, the split into Okapia shortened the neck even further, giving rise to the present-day okapi.

Of course there is still extensive debate as to whether or not this is entirely accurate, other taxonomists have argued that Okapia diverged from the genus Canthumeryx instead. Regardless of how and when exactly the divergence happened, it is accepted by the scientific community that Okapia and Giraffa are sister taxa derived from the same common ancestor. It has been posited that this divergence may have been an example of allopatric speciation, caused in part by the enormous Congo river shifting to create a barrier between two populations. For more information on some of the evolutionary features the okapi shares with the giraffe, click the button below.

Although the giraffe and the okapi are related to each other, with much of their evolutionary history being linked to each other, there are notable differences between the two that warrant the okapi having it's own genus. First, okapi display a sexual dimorphism that sets them apart from giraffes in that only the males of the species develop ossicones. At some point during the divergence of these species the ossicones in female okapi became less and less prominent until they no longer developed at all, this is markedly different from giraffes where both sexes display ossicones throughout their lifetime. Okapi are also one of the few species of mammals where the females are larger than the males.

There is also a couple of slight differences in the skeletons of these two species. Obviously the okapi's neck is a lot shorter than the giraffe's, this is because the cervical vertebrae that make up the neck are not nearly as stretched as the giraffe's, giving the okapi a resemblance closer to that of the giraffe's ancient ancestor than the present-day organism. The okapi has one less tarsal (ankle area) bone in their legs than the giraffe do, possibly this change occurred because the okapi doesn't have nearly as much weight to support as the giraffe does.

Among these major differences are also much smaller changes between the two species. Due to living in a densely forested habitat the okapi has developed a poorer eyesight but greater sense of hearing when compared to the plains-living giraffe. There is also evidence to support the ability for okapi to communicate with low-frequency sounds inaudible to humans, allowing them to more stealthily avoid predators. Okapi have dark fur over the majority of their bodies, with striped fur very similar to that of a zebra over their legs and rump, that allows them to camouflage in the alternating light and shadow among the forest undergrowth.