What Is Life? 2nd Edition by Jay Phelan

Exercise 9

In mammals, the shape of the skull, as well as the shape and size of teeth, often reflects the method of feeding. A skull with a more rounded jaw and shorter, narrower teeth indicates a mammal that is well adapted to pulling bunches of leaves off trees and grinding them up. A skull with a more square jaw indicates a mammal adapted to grazing and cropping vegetation at the ground level. Explain how the adaptations of long, flat teeth and a more square jaw or muzzle could have triggered adaptive radiation in horses.