Question

ordering horse ancestors
paleontologists have discovered several ancestors of
the modern horse.
based on the skeleton, the skull, and the leg bones,
which fossil is the oldest?
which fossil is most like a modern horse?
equus
pliohippus
merychippus
mesohippus

Explanation:

• In horse evolution, older ancestral species are smaller with more primitive skull/leg structures; Mesohippus is the smallest and most anatomically distinct from modern horses, so it is the oldest.
• Equus is the direct modern horse ancestor, matching the modern horse's large body, skull shape, and leg bone structure perfectly, making it the most similar.

Answer:

1. Oldest fossil: Mesohippus
2. Fossil most like modern horse: Equus