On the latter view Merycodus, the prongbuck (Antilocapra) and the antelopes must be regarded as representing three branches from an original common stock, divergent as regards the structure of their cranial appendages, but parallel in other respects.
In view of what has been stated in the preceding paragraph with regard to the extinct American genus Merycodus, it seems, however, at least provisionally advisable to allow the prongbuck to remain as the type of a family - A ntilocapridae.
The Bovidae are thus brought into nearer relationship with the American prongbuck (the only living ruminant which sheds its horn-cover in the adult condition) than has generally been supposed.
Gadow is of opinion that the antlers of the deer, the hornlike protuberances on the skull of the giraffe, and the true horns of the prongbuck and other hollow-horned ruminants (Bovidae) are all different stages of evolution from a single common type: the antlers of the deer being the most primitive, and the horns of the Bovidae the most specialized.
But American extinct types appear to indicate signs of intimate relationship between antelopes, prongbuck and deer, and it may be necessary eventually to amend the current classification.
Either we must regard Merycodus as a deer which parallels the antelopes and the prongbuck in every detail of skeletal structure, or else, like the prongbuck, an antelope separated from the main stock at a date sufficiently early to have permitted the development of a distinct type of cranial appendages, namely, antlers in place of true horns.
The characteristic of this family - as represented by the prongbuck - is that the sheath of the horns is forked, and shed annually, or every few years.