Chordates posses all of the following features at some point of development EXCEPT____________.

Options

A. a dorsal hollow nerve cord
B. a notochord
C. pharyngeal gill slits
D. Amnion

Answer

To answer the question regarding the features that chordates possess at some point in their development, we need to identify the correct features and determine which one does not belong to the chordate characteristics.

### Step-by-Step Solution:

1. **Identify the Features of Chordates**:
Chordates are characterized by four main features during some stage of their development:
- Notochord
- Dorsal hollow nerve cord
- Pharyngeal gill slits
- Post-anal tail

2. **Examine the Options**:
We need to look at the options provided in the question to identify which feature is not characteristic of chordates.

3. **Understand Each Feature**:
- **Notochord**: A flexible rod-like structure that provides support. Present in all chordates at some stage.
- **Dorsal Hollow Nerve Cord**: A nerve cord that runs along the back, which is a defining feature of chordates.
- **Pharyngeal Gill Slits**: These are openings that appear in the throat region and are present at some stage in all chordates.
- **Post-Anal Tail**: A tail that extends beyond the anus, found in chordates during development.

4. **Identify the Exception**:
The amnion is an extra embryonic membrane that is associated with the development of embryos in amniotes (like mammals, birds, and reptiles) but is not a feature that all chordates possess at some point in their development.

5. **Conclusion**:
Therefore, the feature that chordates do not possess at some point in their development is the **amnion**.

### Final Answer:
Chordates possess all of the following features at some point of development EXCEPT **amnion**.

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