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

Options

A. Orohippus, Hyracotherium, Mesohippus, Callipus, Merychippus,Pliohippus,Equus
B. Hyracotherium, Orohippus, Mesohippus, Merychippus,Pliohippus, Equus
C. Orohippus,Callipus,Hyracotherium, Mesohippus,Merychippus, Pliohippus, Equus
D. Hyracotheriu, Mesohippus, Orohippus, Callipus,Merychippus,Pliohippus and Equus.

Answer

To determine the correct sequence in the evolution of the horse, we can break down the evolutionary stages based on the information provided. Here’s a step-by-step solution:

### Step-by-Step Solution:

1. **Identify the First Stage - Hycotherium**:
- The evolution of horses began with the Hycotherium, which existed around 60 million years ago. This was a small, forest-dwelling creature.

2. **Second Stage - Orohippus**:
- Following the Hycotherium, the next stage was the Orohippus, which appeared around 50 million years ago. At this stage, the toes were not yet differentiated.

3. **Third Stage - Mesohippus**:
- The Mesohippus evolved next, approximately 35 million years ago. This species had three toes and was larger than its predecessors.

4. **Fourth Stage - Merichippus**:
- The Merichippus came after the Mesohippus, existing around 15 to 10 million years ago. This species was indigenous to North America and showed further adaptations.

5. **Fifth Stage - Pliohippus**:
- The Pliohippus followed, existing around 5 million years ago. By this time, horses had grown larger and their hooves were more developed.

6. **Modern Horse - Aequus**:
- Finally, the modern horse, known as Aequus, evolved from the Pliohippus around 5 million years ago. This stage represents the fully developed horse we recognize today.

### Correct Sequence:
- The correct sequence in the evolution of the horse is:
1. Hycotherium
2. Orohippus
3. Mesohippus
4. Merichippus
5. Pliohippus
6. Aequus