"notoungulates and condylarths"

GNU Free Documentation LicenseToxodon - Credit: Arthur Weasley
  Notoungulates were hoofed, heavy-bodied mammals from the Paleocene and Pleistocene periods, such as the toxodon (which resembled a rhinoceros).

Condylarths, a mammalian order now extinct, included some of the earliest herbivorous mammals.

Chatwin goes on to list other early creatures present in South America, before the Panamanian landbridge formed allowing North American mammals to outcompete indigenous species: megatherium (an elephant-sized sloth), liptoterns (a grazing beast, similar to a horse), astrapotheriums and the macrauchenia ('like a camel with a trunk').