Canon Paleo Curriculum Unit: 3 Evolution Lesson Plan 10 Page 2

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Part B. Changes in Bone Structures With Time

The changes in horses over the last 55 million years have been shown by studies of

large numbers of fossils. The earliest kind of horse was small and had teeth that were

adapted to browsing on young shoots of trees and shrubs. The present-day horse is

much larger and has larger teeth that are adapted to grazing on the tough leaves of

grasses. Early horses were adapted to living in wooded, swampy areas where more

toes were an advantage. The single-hoofed toes of the present-day horse allow it to

travel fast in the plains.

Examine the diagrams in Figure 2. They show fossils of the front foot bones and

the teeth of horses. The foot bones at the upper right of each diagram indicate

the relative bone sizes of each kind of horse.

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