Why did many grassland mammals evolve long legs for running?

Many grassland mammals evolved long limbs as a specialized adaptation for running, a mode of locomotion known as cursorial movement. This evolutionary development was driven largely by significant climate and environmental changes during the Miocene Epoch, which led to the expansion of open, grassy habitats.123

As these environments became more open, herbivorous mammals faced increased pressure from more efficient predators. To survive, many species evolved long limbs to increase their running speed and effectively escape these threats. Anatomically, these mammals typically possess short, muscular upper legs and thin, elongated lower legs. This structure functions similarly to a pendulum; by reducing the weight at the end of the limb, the animal can increase its speed of oscillation, thereby shortening the duration of each stride and increasing overall velocity.31

In addition to these physical changes, many of these mammals also evolved specialized teeth to graze on gritty grasses, further adapting to the dietary resources available in their new, open grassland ecosystems.3