Some vertebrae of birds are fused to form

Options

A. sacrum
B. synsacrum
C. coccyx
D. none of these

Answer

To answer the question "Some vertebrae of birds are fused to form what?", we can follow these steps:

### Step 1: Understand the options provided
The options given are:
- A) Sacrum
- B) Syn sacrum
- C) Coccyx
- D) None of these

### Step 2: Identify the correct term
In birds, certain vertebrae are fused together to provide structural support and rigidity. This fusion is specifically known as the "syn sacrum."

### Step 3: Explain the composition of the syn sacrum
The syn sacrum is formed by the fusion of:
- 1 posterior thoracic vertebra
- 5 to 6 lumbar vertebrae
- 2 sacral vertebrae
- 5 anterior caudal vertebrae

This fusion creates a compact, triangular skeletal mass that integrates with the pelvic girdle.

### Step 4: Differentiate between the options
- **Sacrum**: While it is related, it does not specifically refer to the fused structure in birds.
- **Coccyx**: This is the tailbone in humans and apes, representing a vestigial tail, but it is not the answer to the question.
- **None of these**: This option is incorrect since we have identified the correct term.

### Step 5: Conclusion
Based on the information, the correct answer is **B) Syn sacrum**.

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