Sharks and dogfishes differ from skates and rays because:

Sharks and dogfishes have cylindrical body while skates and rays have both of their pectoral fins fused. It gives a wing-like appearance and are not distinct from body. Related Theory Sharks have a pectoral fin behind the head on either side of its body. These are ofien elongated and are used to keep the shark from sinking to the bottom of the ocean, as well as for steering the fish. The shark's fins are rigid and elongated. They are supported by cartilaginous, non-segmented rods called ceratotrichia. This strength and rigidity helps the animal to move swifly and with agility. particularly useful when in pursuit of prey that darts away. Rays have flattened disk-like bodies with five gills exit openings and their mouth generally located on their underside. They have large pectoral fins, which they move like wings to travel in the water, and their tails are generally long and slender. with many species having one or more sharp, venomous spines that can be used to inflict painful wounds.