Consider the following characteristics (a) 120 cm high at shoulders (b) Forelimb and hindlimb had one compelete finger and toe and two hidden splints (c) evolved from Mercychippus (d) Teeth adapted for eating grass which of the following ancestral horse is best described by the above mentioned chraracteristics?

Options

A. Pilohiphhus
B. Mesohippus
C. Hyracotherium
D. Callipus

Answer

To solve the question regarding the characteristics of an ancestral horse, we will analyze each characteristic step by step.

### Step-by-Step Solution:

1. **Identify the Characteristics**:
- The characteristics given are:
- (a) 120 cm high at shoulders
- (b) Forelimb and hindlimb had one complete finger and toe and two hidden splints
- (c) Evolved from Merichippus
- (d) Teeth adapted for eating grass

2. **Understand the Evolution of Horses**:
- Horses belong to the family Equidae. The evolution of horses shows a transition from multi-toed ancestors to the modern single-toed horse.
- The evolutionary timeline includes several key species:
- **Hydracotherium**: The earliest known horse-like animal, small and multi-toed.
- **Mesohippus**: Evolved later, still had three toes.
- **Merichippus**: A three-toed horse that lived around 12 to 15 million years ago.
- **Pliohippus**: Evolved from Merichippus and is significant for having one toe (hoof) and teeth adapted for grazing.

3. **Analyze Each Characteristic**:
- **Height (120 cm)**: This height is consistent with Pliohippus, which was larger than its predecessors.
- **Limbs (one complete finger and toe)**: This indicates a transition towards the modern horse's single hoof, which aligns with Pliohippus.
- **Evolution from Merichippus**: Pliohippus directly evolved from Merichippus, making this characteristic a strong indicator.
- **Teeth Adapted for Grass**: Pliohippus had teeth that were more suited for grazing compared to its predecessors.

4. **Select the Correct Option**:
- Based on the analysis, the characteristics described in the question best match **Pliohippus**.
- Other options like Mesohippus and Hieracotherium do not fit the characteristics as they were either earlier in the evolutionary timeline or had different anatomical features.

### Conclusion:
The ancestral horse best described by the mentioned characteristics is **Pliohippus**.

---