In which of the following classes do fish NOT have scales on the body?

Correct option is B

Correct Answer: (b) Holocephalii
Explanation:
→ Holocephalians (chimaeras) lack typical scales on the body, possessing smooth skin instead.
→ This differentiates them from sharks and rays, which have placoid scales.
→ Their bodies are adapted for deep-sea habitats.
Information Booster:
→ They have cartilaginous skeletons and unique tooth plates.
→ Dorsal spine may contain venom.
→ Represent an ancient lineage of Chondrichthyes.
Additional Information (Other Options):
(a) Elasmobranchii – have placoid scales.
(c) Teleostomii – cycloid/ctenoid/ganoid scales.
(d) Dipnoi – have cycloid-like scales.