Non-tetrapod vertebrates contain

Options

A. Osteichytes and chondrichthyes
B. Agnatha, osteichthyes and chondrichthyes
C. Agnatha and chondrichthyes
D. Agnatha

Answer

To answer the question "Non-tetrapod vertebrates contain?", we need to understand the classification of vertebrates and identify which groups fall under non-tetrapods. Here’s a step-by-step breakdown:

### Step 1: Understand the Classification of Vertebrates
- Vertebrates belong to the phylum Chordata.
- Chordata is divided into several subphyla, including protochordates and vertebrates (also known as Eukordata).

### Step 2: Identify the Main Groups of Vertebrates
- The subphylum Vertebrata is divided into two main groups:
1. **Agnatha**: These are jawless vertebrates, which include cyclostomes (like lampreys and hagfish).
2. **Gnathostomata**: These are jawed vertebrates, which can be further divided into:
- **Pisces**: This includes both cartilaginous fishes (Chondrichthyes) and bony fishes (Osteichthyes).
- **Tetrapoda**: This group includes vertebrates with four limbs (like amphibians, reptiles, birds, and mammals).

### Step 3: Define Non-Tetrapod Vertebrates
- Non-tetrapod vertebrates are all vertebrates that are not classified as tetrapods. This includes:
- **Agnatha** (jawless fishes)
- **Chondrichthyes** (cartilaginous fishes)
- **Osteichthyes** (bony fishes)

### Step 4: Evaluate the Options
- The options provided are:
1. Ostichthyes and Chondrichthyes
2. Agnatha, Ostichthyes, and Chondrichthyes
3. Agnatha and Chondrichthyes
4. Agnatha

- Since non-tetrapod vertebrates include all three groups (Agnatha, Chondrichthyes, and Osteichthyes), the correct answer is **Option 2: Agnatha, Osteichthyes, and Chondrichthyes**.

### Final Answer
Non-tetrapod vertebrates contain **Agnatha, Osteichthyes, and Chondrichthyes**.

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