This book provides the first extensive documentation of vertebrate evolution in tropical South America, as deciphered from a complex of well-worked Miocene fossil sites in Colombia. These sites, known collectively as La Venta, constitute a unique record of this tropical vertebrate palaeofauna and an unprecedented picture of the ancient biodiversity of South America. The geological, biological and environmental evidence found at La Venta includes the earliest recorded occurrences of some modern mammals, birds, and fishes, as well as indications of many species new to science. The book describes the fossils, group by group, interpreting their phylogeny and palaeobiology, and placing them in a temporal and geologic framework.