The following group is not a subphylum of Chordata

Options

A. Urochordata
B. Tetrapoda
C. Cephalochordata
D. Vertebrata

Answer

To determine which group is not a subphylum of Chordata, we need to analyze the given options. Here are the steps to arrive at the solution:

### Step-by-Step Solution:

1. **Identify the Subphyla of Chordata**:
- Chordata is divided into three primary subphyla:
- Urochordata (or Tunicata)
- Cephalochordata
- Vertebrata

2. **Examine the Options**:
- The question provides several groups, one of which is not a subphylum of Chordata. We need to evaluate each option against the known subphyla.

3. **Analyze Urochordata**:
- Urochordata, also known as Tunicata, is indeed a subphylum of Chordata. It includes marine animals like sea squirts.

4. **Analyze Cephalochordata**:
- Cephalochordata includes lancelets, which are also classified under Chordata. Thus, this is a valid subphylum.

5. **Analyze Vertebrata**:
- Vertebrata is the subphylum that includes animals with a backbone, such as mammals, birds, reptiles, amphibians, and fish. This is also a recognized subphylum of Chordata.

6. **Analyze Tetrapoda**:
- Tetrapoda refers to a superclass or clade that includes four-limbed vertebrates (amphibians, reptiles, birds, and mammals). However, it is not classified as a subphylum but rather as a grouping within the subphylum Vertebrata.

7. **Conclusion**:
- Since Tetrapoda is not a subphylum of Chordata but rather a clade within the Vertebrata subphylum, it is the correct answer to the question.

### Final Answer:
The group that is not a subphylum of Chordata is **Tetrapoda**.