In the geological history of earth, the beginning of birds and mammals occurred in

Options

A. Carboniferous and Permian epochs
B. Jurassic
C. Silurian
D. Eocene and Oligocene

Answer

**Step-by-Step Solution:**

1. **Understanding the Geological Time Scale**: The geological history of Earth is divided into several eras and periods. The Mesozoic Era is particularly important for the evolution of birds and mammals.

2. **Identifying the Relevant Periods**: The question asks about the beginning of birds and mammals. The options provided are:
- Carboniferous and Permian
- Jurassic
- Saurian
- Eocene and Oligocene

3. **Focusing on the Jurassic Period**: The Jurassic period is known for significant evolutionary developments, including the rise of dinosaurs and the emergence of early birds and mammals.

4. **Time Frame of the Jurassic Period**: The Jurassic period occurred approximately 199.6 million years ago to 145.5 million years ago. It follows the Triassic period and precedes the Cretaceous period.

5. **Examples of Early Birds and Mammals**:
- **Archaeopteryx**: This is considered the first bird, which appeared around 150 million years ago towards the end of the Jurassic period.
- **Early Mammals**: An example is Adelobacillus, a shrew-like creature that had differentiated ear and jaw bones, indicating early mammalian traits.

6. **Eliminating Incorrect Options**:
- The **Carboniferous and Permian** periods occurred before the Jurassic and are not associated with the beginnings of birds and mammals.
- The **Saurian** period is not a recognized geological period in the context of bird and mammal evolution.
- The **Eocene and Oligocene** periods occurred after the Jurassic and are associated with the diversification of mammals and birds, not their origin.

7. **Conclusion**: Based on the evidence and examples provided, the correct answer is that the beginning of birds and mammals occurred in the **Jurassic period**.

**Final Answer**: The beginning of birds and mammals occurred in the **Jurassic period**.

---