At twenty-one minutes to midnight they vanish and the age of mammals begins.

Hence the Tertiary period may be called "the age of mammals."

Still higher, or more recent, are Cuvier and Brongniart's tertiary rocks, representing the age of mammals.

Then came the Caenozoic age , or age of mammals, three million years, with strata thirty-one hundred feet thick.

The age of mammals awaited the deepening and the enrichment of the soil and the stability of the earth's crust.

They were the dominant land animals of their time, just as the quadrupeds were during the Age of Mammals.

We think we're at the end of the Age of Mammals, and well into the Age of Managing the Ecology.

From between the feet of stomping dinosaurs, ratty animals scurry about; cue an asteroid impact and the Age of Mammals begins.

Thus, since vertebrates appeared, we have in succession the Age of Fishes, the Age of Amphibians, the Age of Reptiles, and the Age of Mammals.