Evolutionary radiation

[2] A significantly large and diverse radiation within a relatively short geologic time scale (e.g. a period or epoch) is often referred to as an explosion.

[3] Perhaps the most familiar example of an evolutionary radiation is that of placental mammals immediately after the extinction of the non-avian dinosaurs at the end of the Cretaceous, about 66 million years ago.

At that time, the placental mammals were mostly small, insect-eating animals similar in size and shape to modern shrews.

[9] Much of the work carried out by palaeontologists studying evolutionary radiations has been using marine invertebrate fossils simply because these tend to be much more numerous and easy to collect in quantity than large land vertebrates such as mammals or dinosaurs.

In places such as Lake Malawi they have evolved into a very wide variety of forms, including species that are filter feeders, snail eaters, brood parasites, algal grazers, and fish-eaters.