All the World's Antelopes: Reedbuck and Rhebok

Bohor reedbuck

Quite where, within the larger bovid family, the reedbucks belong was long a matter of contention. They are medium-sized antelopes, tending to prefer habitats with plenty of water, distinguished by the fact that not only their visible horns, but also the bony cores on the inside, have transverse ridges running round them. The detailed structure of their teeth has some resemblance to that of the true bovines (that is, cows, bison, and the like) but it's hard to see that as anything other than parallel evolution. 

The most widely followed scheme in the late 20th century placed them with the grazing antelopes, such as sables and their kin, but even then there was a suspicion that this was only because nobody knew what else to do with them. Once we were able to do detailed genetic analysis, it turned out that they are pretty much in a group of their own, not especially close to anything, having diverged from the ancestors of the true grazing antelopes before that group diverged from the goats. Our best guess is that this happened between 16 and 14 million years ago; there are antelopes with longer lineages, but not many.