Consider the following statements :-
(1) Protochordates are exclusively marine
(2) In cephalochordates, Notochord extends from head to tail region
(3) In urochordates, Notochord is present only in larval tail
(4) Cranium and vertebral column are bony in cyclostomates
Which of the above statement is/are correct?

Options

A. 1 alone
B. 2, 3 and 4
C. 1, 2 and 3
D. All of these

Answer

To determine which statements about protochordates and related groups are correct, let's analyze each statement step by step.

### Step-by-Step Solution:

1. **Statement 1: Protochordates are exclusively marine.**
- **Analysis:** Protochordates, which include groups like cephalochordates and urochordates, are primarily marine organisms. They are typically found in oceanic environments.
- **Conclusion:** This statement is **correct**.

2. **Statement 2: In cephalochordates, notochord extends from head to tail region.**
- **Analysis:** Cephalochordates, such as lancelets, possess a notochord that runs the length of their body from the head to the tail. This structure is a defining characteristic of this group.
- **Conclusion:** This statement is **correct**.

3. **Statement 3: In urochordates, notochord is present only in larval tail.**
- **Analysis:** Urochordates, such as tunicates, have a notochord that is present only in the larval stage, specifically in the tail region. In the adult form, the notochord is typically lost or reduced.
- **Conclusion:** This statement is **correct**.

4. **Statement 4: Cranium and vertebral column are bony in cyclostomates.**
- **Analysis:** Cyclostomates, which include jawless fish like lampreys and hagfish, have a cartilaginous cranium and vertebral column. They do not possess a bony structure; instead, their skeletons are made of cartilage.
- **Conclusion:** This statement is **incorrect**.

### Final Evaluation:
- **Correct Statements:** 1, 2, and 3 are correct.
- **Incorrect Statement:** 4 is incorrect.

### Answer:
The correct statements are 1, 2, and 3.

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