Dino Shark Surfaces

You're looking at a sight rarely seen--a 5-foot (1.5-meter) frilled shark, a living specimen of an ancient species once thought extinct. She doesn't look happy to see you, but don't take offense. Frilled sharks avoid the spotlight.

This "living fossil" flared her gills for the cameras last week at Japan's Awashima Marine Park, but she wasn't there to show off. The park's staff brought her in after a fisherman alerted them to a "strange eel-like fish with razor sharp teeth" swimming nearby. She died a few hours after being captured, and was likely sick before she wound up at the surface.

Frilled sharks normally stay well beneath the waves--at depths of a few hundred to a few thousand feet (120 to 1,280 meters). There, they use rows of razor-sharp, trident-like teeth to feed on squid, bony fish, and other sharks. They can grow to more than 6 feet (2 meters) in length and are thought to have changed little since prehistoric times.

In that, they're like most sharks. Scientists have identified more than 350 species of sharks alive today, and most live more or less as their ancestors did 200 million years ago--long before T-rex began his reign of terror on land. Still, seeing a frilled shark is special. They're one of the few surviving species from one of the oldest shark orders, and so unique that some scientists give them an order of their own.

In addition to their "frills"--really, tissue protruding from six gill slits--frilled sharks are distinguished by their eelish figures (see it) and terminal mouths. Terminal mouths? For fish scientists, a terminal mouth is just one that "opens at the anterior end of the head with upper and lower jaws equal" (see it). Squid may have a different definition.

Now Meet the Great White Hunters

Imagine you're a seal, a turtle, or some other fine-flavored denizen of the deep. Now imagine a great white shark is on your tail. Friend, you're in a sea of trouble. Here's why.