Which peculiar types of system is found only in the echinodermates?

Explanation

### Step-by-Step Solution:

1. **Identify the Group**: The question asks about a peculiar type of system found only in echinoderms. Echinoderms are a specific group of marine animals.

2. **Define Echinoderms**: Echinoderms are characterized by their spiny skin and include organisms such as starfish, sea urchins, and sea cucumbers. They are exclusively marine and belong to the phylum Echinodermata.

3. **Key Feature**: The most distinctive feature of echinoderms is the presence of the **water vascular system**. This is a unique system that is not found in other animal groups.

...