Which of the following organisms is known to be a jawless vertebrate ?

Options

A. Petromyzon
B. Scoliodon
C. Pristis
D. Trygon

Answer

To determine which of the following organisms is known to be a jawless vertebrate, we will analyze the options provided and identify the characteristics of each organism.

### Step-by-Step Solution:

1. **Identify the Organisms**: The options given are:
- Petromyzon (Lamprey)
- Scoliodon (Shark)
- Terris (Turtle)
- Trigon (Stingray)

2. **Classify the Organisms**:
- **Petromyzon (Lamprey)**: This organism belongs to the superclass Agnatha, which is characterized by the absence of jaws. Lampreys have a circular mouth and lack true jaws or bones.
- **Scoliodon (Shark)**: This organism is a type of shark and belongs to the superclass Gnathostomata, which includes all jawed vertebrates. Sharks have well-developed jaws.
- **Terris (Turtle)**: Turtles also belong to the superclass Gnathostomata, meaning they possess jaws.
- **Trigon (Stingray)**: Like sharks and turtles, stingrays are also part of Gnathostomata and have jaws.

3. **Conclusion**: Among the options, only Petromyzon (Lamprey) is classified as a jawless vertebrate. The other organisms (Scoliodon, Terris, and Trigon) all have jaws.

### Final Answer:
The organism known to be a jawless vertebrate is **Petromyzon (Lamprey)**.

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