T
his chapter examines the evolution of the mammals and the chang-
ing landscapes during the Tertiary period. The Cenozoic era, begin-
ning 65 million years ago, is synonymous with the “age of mammals.”
Because of their great diversity, many more species of plants and animals are
alive today than at any other time in geologic history.The appearance of the
grasses early in the period spawned the evolution of ungulates or hoofed ani-
mals and voracious carnivores to prey on them. The prosimians (pre-apes)
were also on the scene and gave rise to the anthropoids, the ancestors of apes
and humans.
Extremes in climate and topography created a greater variety of living
conditions than at any other equivalent span of geologic time. The rigorous
environments presented many challenging opportunities for plants and ani-
mals.The extent to which they invaded diverse habitats was truly remarkable.
This was a time of continuous change.All species had to adapt to a wide range
of living conditions. The changing climate patterns resulted from the move-
ment of continents toward their present positions and from the intense
mountain building that raised most ranges of the world.TERTIARY MAMMALS
THE AGE OF ADVANCED SPECIES