Some of the land reptiles went back into the water to evolve into
fish-like reptiles (e.g. Ichthyosaurs), probably around

Options

A. 200 mya
B. 500 mya
C. 100 mya
D. 1 bya

Answer

To solve the question regarding when some land reptiles evolved into fish-like reptiles such as Ichthyosaurs, we can follow these steps:

1. **Identify the Organisms**: The question mentions "fish-like reptiles" and specifically refers to Ichthyosaurs. Ichthyosaurs are known to be marine reptiles that resemble fish.

2. **Understand Their Evolution**: It is important to note that Ichthyosaurs evolved from land reptiles that returned to the aquatic environment. This indicates a significant evolutionary transition.

3. **Determine the Time Frame**: The options provided are 200 million years ago, 500 million years ago, 100 million years ago, and 1 billion years ago. We need to identify the correct time frame for the evolution of Ichthyosaurs.

4. **Research Historical Context**: Ichthyosaurs are believed to have first appeared during the Mesozoic Era, specifically in the Triassic period, which began around 250 million years ago and lasted until about 200 million years ago.

5. **Narrow Down the Options**: Given that Ichthyosaurs are known to have evolved around the early Mesozoic Era, the most accurate option from the choices provided is 200 million years ago.

6. **Conclude the Answer**: Therefore, the correct answer to the question is that some land reptiles went back into the water to evolve into fish-like reptiles (Ichthyosaurs) probably around 200 million years ago.