Following chordata is not a vertebrate

Options

A. Branchiostoma
B. Petromyzon
C. Salamander
D. Buto

Answer

To determine which chordate is not a vertebrate, we can analyze the given options based on their classification within the phylum Chordata.

### Step-by-Step Solution:

1. **Understanding Chordata**: The phylum Chordata includes all animals that have a notochord at some stage of their development. This group is divided into two main subphyla: Vertebrata (vertebrates) and Non-vertebrate chordates.

2. **Identifying the Options**: The question provides four options, one of which is Brachyostoma (also known as Amphioxus). We need to evaluate each option to determine if it is a vertebrate or not.

3. **Analyzing Brachyostoma**:
- Brachyostoma is classified as a Cephalochordate.
- Cephalochordates are characterized by having a notochord that extends from head to tail, but they do not possess a backbone or vertebrae.
- Therefore, Brachyostoma is not a vertebrate.

4. **Evaluating Other Options**:
- Petromyzon (lamprey) is a cyclostome and is classified as a vertebrate because it has a rudimentary vertebral column.
- Salamanders are amphibians and also possess a vertebral column, thus they are vertebrates.

5. **Conclusion**: Based on the analysis, Brachyostoma is the only option that is not a vertebrate.

### Final Answer:
The following chordate that is not a vertebrate is **Brachyostoma**.