The earliest fossil form in the phylogeny of horse is

Options

A. Merychippus
B. Mesohippus
C. Eohippus
D. Equus.

Answer

To answer the question about the earliest fossil form in the phylogeny of the horse, we will follow these steps:

### Step-by-Step Solution:

1. **Identify the Options**: The question provides four options:
- 1st: Merichippus
- 2nd: Mesohippus
- 3rd: Eohippus
- 4th: Equus

2. **Understand the Phylogeny of Horses**: The phylogeny of horses traces their evolutionary history. It is important to identify the earliest known horse-like creature.

3. **Research Each Option**:
- **Merichippus**: An extinct proto-horse from the family Equidae, known to have lived during the Miocene period. It is not the earliest form.
- **Mesohippus**: An early horse that existed around 40 to 30 million years ago, during the middle Eocene to early Oligocene. This is also not the earliest form.
- **Eohippus**: Known as the "Dawn Horse," this is recognized as the earliest known horse, belonging to the genus Hyracotherium. It lived during the early Eocene epoch, approximately 56 to 33.9 million years ago.
- **Equus**: This is the modern genus that includes horses, donkeys, and zebras. It is not an early fossil form.

4. **Determine the Correct Answer**: Based on the research, Eohippus is the earliest fossil form in the phylogeny of horses.

5. **Final Answer**: The earliest fossil form in the phylogeny of the horse is **Eohippus**.