Sharks and dogfishes differ from skates and rays because
- gill slits are ventrally placed
- head and trunk are widened considerably
- distinct demarcation between body and tail
- their pectoral fins distinctly marked off from cylindrical bodies.
Answer
(4) their pectoral fins distinctly marked off from cylindrical bodies.
Solution
Sharks and dogfishes ( Scoliodon) have a spindle-shaped, cylindrical body with pectoral fins distinctly marked off from the body and laterally placed gill slits.
⇒ Skates and rays ( Trygon, Torpedo) have a dorsoventrally flattened body; their large pectoral fins are fused with the sides of the head and trunk, and the gill slits are ventral.
∴ Sharks and dogfishes differ in having pectoral fins distinctly marked off from their cylindrical bodies.
Answer: (4)