EVOLUTION OF HORNS IN UNGULATES: ECOLOGY AND PALEOECOLOGY - JANIS - 2008 - Biological Reviews - Wiley Online Library

EVOLUTION OF HORNS IN UNGULATES: ECOLOGY AND PALEOECOLOGY - JANIS - 2008 - Biological Reviews - Wiley Online Library: "The savanna ungulate faunas of the North American Miocene were broadly similar to those of present-day East Africa in terms of overall morphological and taxonomic diversity. However, the predominant ungulates of the African faunas are bovids, which possess bony horns that are primitively sexually dimorphic in their occurrence. The predominant ungulates of the North American Tertiary were equids, camelids and oreodonts, which all lacked horns. A limited number of horned ruminants were present, but these were largely Miocene immigrants from Eurasia. Horns were also absent from the large-bodied herbivores in the endemic faunas of South America and Australia."