Using fossil evidence, scientists can learn how organisms have changed over long periods of time. The chart shows information about how traits of ancestors of the modern horse have changed.
5
(а)
Identify the species of horse fossils that would be found in the uppermost layer of rock and in the bottommost layer of rock.
Part A
Species of fossil found in uppermost layer of rock:
Characteristics of Four Horse Species
Horse
Species
Estimated
Time When
Present
Characteristics
Hyracotherium
55 million years ago
Small, fox-sized animal with a short face and low-crowned teeth
Orohippus
45-52 million years ago
Similar in size to Hyracotherium but with a slimmer body, slimmer legs, and a longer head
Mesohippus
32-37 million years ago
Taller and longer than
Orohippus; eyes rounder and set wider apart and farther back than those of Hyracotherium
Miohippus
25-32 million years ago
Larger than Mesohippus, with a longer head and extra material on its upper molars, which allowed it to chew tougher plants
Species of fossil found in uppermost layer of rock: Miohippus
Species of fossil found in bottommost layer of rock: Hyracotherium