Like sharks, their skeletons are made of cartilage instead of bones. Cartilaginous fish belong to the class of fishes known as Chondrichthyes . Most rays are kite-shaped with streamlined tails that may have one or more poisonous barbs or spines. In contrast, skate tails are fleshier and heavier, and have small fins. In general, skates commonly found in North American waters have elongated noses.
Size is another way to differentiate rays from their skate cousins.
Rays can grow to tremendously large sizes. The five species of skates commonly found in North Carolina waters range in size from 16 inches to 5 feet in length. Rays and skates use different mechanisms to defend themselves, too. The stinging spine on the ray's tail is an effective weapon against predators. The edges of the spine are serrated so that once driven into a victim it is very difficult to remove without creating more damage.