As horse evolved, there was progressive reduction in the number of toes. Which of the following is the correct sequence in the evolution of horse ?

Options

A. Orophippus, Hyracotherium, Mesophippus, Callipus, Merychippus, Pliophippus, Equus
B. Hyracotherium, Orophippus, Mesophippus, Merychippus, Pliohippus, Equus
C. Orophippus, Callipus, hyracotherium, Mesophippus, Merychippus, Pliohippus, Equus
D. Hyracotherium , Mesohippus, Orohippus , Gallipus, Merychippus, Pliohippus, and Equus

Answer

To determine the correct sequence in the evolution of horses, we need to understand the lineage and the progressive reduction in the number of toes over time. Here is the step-by-step solution:

1. **Identify the Starting Point**: The evolution of the horse begins with the earliest ancestor known as **Hyracotherium**. This species lived during the Eocene epoch and is considered the first horse-like creature.

2. **Progression to Orohippus**: After Hyracotherium, the next significant species in the evolutionary line is **Orohippus**, which also lived during the Eocene epoch. This species shows some adaptations towards a more horse-like form.

3. **Evolution to Mesohippus**: The next step in the evolution is **Mesohippus**, which appeared during the Oligocene epoch. This species had a further reduction in the number of toes and was larger than its predecessors.

4. **Advancement to Myohippus**: Following Mesohippus, we have **Myohippus**, which also existed in the Oligocene epoch. Myohippus exhibited more advanced features and a further reduction in toe number.

5. **Transition to Parahippus**: The next species is **Parahippus**, which lived during the Miocene epoch. This species shows more adaptations towards grazing and had a more horse-like structure.

6. **Evolution to Merychippus**: After Parahippus, we have **Merychippus**, which also existed in the Miocene epoch. Merychippus is significant because it had a more developed limb structure and further reduced toes.

7. **Progression to Hipparion**: The next species is **Hipparion**, which lived during the Miocene to Pliocene epochs. Hipparion had a more modern appearance and was adapted for running.

8. **Advancement to Pliohippus**: After Hipparion, we have **Pliohippus**, which lived during the Pliocene epoch. This species is often considered a direct ancestor to modern horses.

9. **Final Stage - Equus**: The last in this evolutionary line is **Equus**, which includes the modern horse and appeared during the Pleistocene epoch. Equus represents the culmination of the evolutionary changes that occurred over millions of years.

### Correct Sequence of Evolution:
- Hyracotherium → Orohippus → Mesohippus → Myohippus → Parahippus → Merychippus → Hipparion → Pliohippus → Equus