Q.Draw neat labelled diagram: Scolidon

Cartilaginous fishes are jawed vertebrates with paired fins and placoid scales, whereas living jawless fishes lack jaws, lack paired fins, and lack scales — reflecting their more primitive body plan.

Comparing Class Chondrichthyes (cartilaginous fishes, e.g., sharks, rays, skates) with the living jawless fishes of Superclass Agnatha/Class Cyclostomata (e.g., lampreys, hagfish):

• Jaws: Cartilaginous fishes possess true, movable jaws (they are gnathostomes), allowing active predation/biting. Jawless fishes, as their name states, completely lack jaws; their mouth is a simple round, sucking/rasping structure.
• Paired fins: Cartilaginous fishes have well-developed paired pectoral and pelvic fins. Jawless fishes lack paired fins entirely; they have only median (unpaired) fins.
• Body covering: Cartilaginous fishes are covered with placoid scales (small, tooth-like dermal scales). Jawless fishes have smooth, naked (scaleless) skin, often covered in mucus.
• Gill openings: Cartilaginous fishes typically have 5-7 pairs of exposed gill slits opening directly to the exterior. Jawless fishes have a series of gill pouches (round gill openings/pores, sometimes more numerous, e.g., up to 14-15 pairs in some hagfish). …