The anatomy of an angel shark

HowStuffWorks

Angel Shark Anatomy

As we mentioned, the angel sharks live up to their "squatty" name, with most species of squatina measuring only about 5 feet (1.5 meters). A few species, such as the Japanese angel shark and the Mediterranean angel shark, may be as long as 6.5 feet (2 meters), but that's about as long as they get. While most weigh about 60 pounds (27 kilograms), the biggest angel shark, found in Europe, has been known to weigh 170 pounds (77 kilograms) [source: Lineaweaver].

Angel sharks look more like rays than great whites, but they have all the same basic equipment as sharks. It just happens that the equipment is flattened dorsoventrally, or from top to bottom. The pectoral fins that give the angel shark its name are probably the first thing to strike your eye. To review, these fins aren't attached to the head, as they are in rays. The pelvic fins are similarly flattened and expand outward from the body.

The mouth is located at the very tip of the snout, and inside are some truly scary teeth. Shaped like triangles, the teeth are extremely sharp and come to needlelike points. On either side of the mouth are barbels, which are whiskerlike antennae that sniff out the chemical reactions of prey along the bottom of the ocean floor.

Along the side of the head are gill slits that allow the angel shark to breathe. The positioning of the gill slits represents another important distinction from rays and skates, which have gill slits on the bottom of their heads. Unlike many other sharks that must constantly swim to pull water over their gill slits, the angel shark uses its muscles to pull water over the gill slits while in a resting position. This shark also has a spiracle, or a tube behind the eyes that can pull in water when the shark's mouth is closed.

One way that angel sharks do differ from other sharks is their caudal fin, or tail. Most sharks' tails are top-heavy, meaning that the top lobe of the fin is bigger than the second one. The opposite holds true for angel sharks. They have a longer lower lobe, which may help them achieve a quick liftoff when they attack their prey from below.

A successful attack from below is the key to an angel shark's next meal. Many of the angel shark's features, from its flattened body to its barbels to a tail that helps it move upward quickly, allow it to live at the bottom of the ocean floor, waiting for prey to swim by. Even its coloring provides camouflage. Angel sharks are various shades of white, gray, brown and black, colors that blend in with the ocean floor. Some have red spotting, which may provide even more coordination with their habitat.

Find out where they're lying in wait, and what exactly they're waiting for, on the next page.