During the tertiary period the ancestors of modern horses and cattle evolved with adaptations for eating what new source?

During the Tertiary period, the ancestors of modern horses and cattle evolved adaptations for grazing on grasses, which became more abundant due to the expansion of grasslands. These adaptations included elongated limbs for running, specialized teeth for grinding tough plant material, and changes in digestive systems to process fibrous grasses efficiently. The shift from browsing on woody plants to grazing on grass was crucial for their survival and success in changing ecosystems.