We describe Paratoceras tedfordi, a new species of Protoceratidae from early Miocene amber-bearing sands near Simojovel, Chiapas, southern Mexico. The holotypic cranium weakly expresses maxillary plates, supraorbital rugosities, and a median occipital projection as in the type of Paratoceras wardi, and is interpreted as a female. Its short facial region, elongate premolars, and brachydont molars place it among the Protoceratinae, not Synthetoceratinae. We also describe new cranial and the first postcranial material of Prosynthetoceras texanus from Alum Bluff and Thomas Farm sites in Florida. Incorporating data from these new specimens, we consider highlights of protoceratid adaptive morphology including their elaborate male ossicones, tapirlike proboscis, brachydont to mesodont dentition, and limb features and proportions. We suggest that progressive protoceratids may be seen as ecological analogues of the Bushbuck of South Africa, a forest-adapted browser. Each of the three groups of horned Protoceratidae speciated allopatrically along latitudinal lines, with the northern branch becoming extinct earlier than its southern sister. Their greater proclivity toward survival in tropical latitudes explains the importance of Protoceratidae in the Gulf Coastal Plain during the Miocene, and evident higher abundance of Paratoceras in Central America.