What are urochordates? Give one example.

Explanation

### Step-by-Step Solution:

1. **Definition of Urochordates**:
Urochordates, also known as tunicates, are a subphylum of the phylum Chordata. They are characterized by their unique features that distinguish them from other chordates.

2. **Primitive Characteristics**:
Urochordates are considered lower chordates, meaning they possess primitive structures that are not found in more advanced chordates. This includes the presence of a notochord, which is a flexible rod-like structure that provides support.

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