Which of the following bones is present only in birds ?

Options

A. Axis vertbra
B. Atlas vertebra
C. Ear ossicles
D. Furcula

Answer

To determine which bone is present only in birds, we will analyze each option provided in the question.

1. **Axis vertebrae (Option A)**:
- The axis vertebra is part of the vertebral column and is present in many vertebrates, including mammals. Therefore, it is not exclusive to birds.

2. **Atlas vertebrae (Option B)**:
- The atlas vertebra is also part of the vertebral column and is found in various vertebrates, including mammals. Thus, it is not unique to birds.

3. **Ear ossicles (Option C)**:
- Ear ossicles are small bones found in the middle ear of mammals. These bones are not present in birds, making this option incorrect as well.

4. **Furcula (Option D)**:
- The furcula, commonly known as the wishbone, is a bone found in birds. It is formed by the fusion of two clavicles and is unique to birds, providing structural support during flight.

Based on this analysis, the bone that is present only in birds is **Option D: Furcula**.