Which is a missing link between birds and reptiles

Options

A. Struthio
B. Casuarias
C. Apterynx
D. Archaeopteryx

Answer

To determine the missing link between birds and reptiles, we can analyze the options provided:

1. **Struthio**: This is a genus of birds that includes ostriches. While ostriches are flightless birds, they do not represent a transitional form between birds and reptiles.

2. **Casuarius**: This genus includes cassowaries, which are also large, flightless birds. Similar to Struthio, cassowaries do not serve as a link between birds and reptiles.

3. **Apteryx**: This is the genus for kiwis, which are flightless birds native to New Zealand. Like the previous two options, kiwis do not represent a transitional form between birds and reptiles.

4. **Archaeopteryx**: This is widely recognized as the transitional fossil between birds and reptiles. First described in 1861, Archaeopteryx exhibits features of both theropod dinosaurs and modern birds, making it a significant link in the evolutionary chain.

Based on this analysis, the correct answer is **Archaeopteryx**.

### Step-by-Step Solution:
1. **Identify the options**: Look at the four options given: Struthio, Casuarius, Apteryx, and Archaeopteryx.
2. **Analyze each option**:
- Struthio: A genus of ostriches, not a transitional form.
- Casuarius: A genus of cassowaries, also not a transitional form.
- Apteryx: Kiwis, which are flightless birds, not a transitional form.
- Archaeopteryx: Recognized as a transitional fossil between birds and reptiles.
3. **Conclude**: Archaeopteryx is the missing link between birds and reptiles.