Mammal Faunas of Xeric Habitats and the Great American Interchange

Abstract

The Great American Interchange is one of the more fascinating occurrences in vertebrate history. A huge continent, South America, was cast adrift from the terrestrial mainland of the Gondwana supercontinent very early in mammalian history. Like a massive island, South America moved slowly northward at a rate of only centimeters per year, its initial faunal complement developing in isolation from the rest of the organisms of the world. Detailed reports on the evolution of the South American paleofauna during this period are available elsewhere (e.g., G. G. Simpson, 1967, 1969, 1978, 1980; Patterson and Pascual, 1972; Webb, 1976; Marshall et al., 1979, 1981, 1982; Webb and Marshall, 1982) and will not be reviewed extensively here. I will examine only some highlights of the interchange to illustrate factors that are important to the development of the faunas of arid and semiarid habitats. Suffice to say that the evolution of mammals in South America took place over both space and time.