Which of the following is not a protochordate?

Options

A. Herdmania
B. Amphioxus
C. Salpa
D. Petromyzon

Answer

To determine which of the following is not a protochordate, we need to understand the classification of animals within the phylum Chordata. Protochordates are typically classified into two main groups: Urochordata and Cephalochordata.

Here’s a step-by-step solution:

1. **Understand the Definition of Protochordates**: Protochordates are simple chordates that include two subphyla: Urochordata (tunicates) and Cephalochordata (lancelets). They possess a notochord at some stage of their life cycle.

2. **Identify the Options**: The question provides several options, which we need to evaluate to see which one does not belong to the protochordate group.

3. **Analyze Each Option**:
- **Herdmania**: This organism is a type of tunicate and falls under Urochordata, hence it is a protochordate.
- **Amphioxus**: Commonly known as lancelet, it belongs to Cephalochordata, making it a protochordate as well.
- **Salpa**: This is another type of tunicate, which also belongs to Urochordata, thus it is a protochordate.
- **Petromyzon (Lamprey)**: This organism belongs to the class Cyclostomata, which includes jawless fish. It does not fall under the protochordate category.

4. **Conclusion**: Since Petromyzon (Lamprey) is the only organism that does not belong to the protochordate group, it is the correct answer to the question.

**Final Answer**: Petromyzon (Lamprey) is not a protochordate.