Question

Which of the following vertebrate classes is jawless?

• A. Chondrichthyes
• B. Osteichthyes
• C. Trygon & Aves
• D. Cyclostomata

Hint:

Remember: \[ \boxed{\text{Cyclostomata} \rightarrow \text{Jawless vertebrates}} \] Examples: \[ \boxed{\text{Petromyzon and Myxine}} \] All other classes of fishes possess true jaws.

Answer 1

The Correct Option is D

Cyclostomata (class Agnatha) are the most primitive living vertebrates, characterised by the complete absence of jaws, paired fins, and a cartilaginous skeleton. Lampreys (Petromyzon) and hagfish (Myxine) are the two representative members, and they are ectoparasites or scavengers with a circular sucking mouth.