The Rise and Reign of the Mammals: A New History, from the Shadow of the Dinosaurs to Us

two key features of mammals. The olfactory bulbs—which orchestrate the sense of smell—are massive. And the top of the cerebrum boasts a new structure: a six-layered mass of nervous tissue called the neocortex,

The dirt and phytoliths function as sandpaper, filing down the teeth of grazing mammals as they eat.

The head was repositioned to sit atop the neck instead of sticking out in front of it.

changes involves the brain: it often gets smaller, probably to save energy, because big brains are expensive to maintain.

with an all-you-can-eat buffet of greenery that grew, constantly, from the soil.

their amniotic eggs, with membranes to nourish, protect, and keep their embryos moist. They moved freely across the land, establishing connections between regions that were previously isolated, and in doing so, evolving new species, new body types, larger size, new diets, new behaviors.

The backbone, which is horizontally oriented and perpendicular to the hind limbs in horses and mice and whales and basically all other mammals, rotated to become parallel to the legs, and took on a curved shape.

Whatever they were, they weren’t unique to us. Later anatomists identified this same three-bone set in other mammals—but only mammals.

triggered a profound change in the mammals that lived on them,