4. The radiation of mammals

Abstract

For two-thirds of their entire history, right through the 135 million years left of the Mesozoic Era, mammals were all small, secretive animals feeding at night on insects, worms, seeds, and plant tubers. Mammals were restricted in size due to their competition with the dinosaurs. But mammalian evolution continued and early examples of placentals and marsupials have been dated to this period. ‘The radiation of mammals’ outlines the end-Cretaceous mass extinction period 65 mya when over 60 per cent of all living species disappeared. It also describes the Tertiary radiation of mammals through changing climates, and the mammalian evolution on the island continents of Australia and South America.