Sharks have five to seven gill slits on each side of their head.

The goblin shark (Mitsukurina owstoni) is the only extant representative of the family Mitsukurinidae, a lineage some 125 million years old.

The Portuguese dogfish has been reported at depths of 150 m (490 ft) to 3,675 m (12,057 ft) from the lower continental slope to the abyssal plain, making it the deepest-living shark known.

At 40 feet long, the whale shark can weigh as much as 13 tons, which is the same as two African elephants!

Litters of up to 135 pups have been reported. That's a lot of mouths to feed!

There are over 400 species of sharks, from the 8-inch-long dwarf lanternshark to the 40-foot-long whale shark.

Male sharks have to bite the head, gill or pectoral fin region of the female in order to mate. Not only that, they also have to hold on for several minutes, leaving female sharks with scars after mating season.

93% of unprovoked great white shark attacks are on males and 5% on females, while the sex of the remaining 2% of victims cannot be determined. Why do great whites prefer gentleman? Probably because they're more likely to do stupid things!

Sharks are older than trees. The earliest species that can reasonably be classified as a tree, the now-extinct Archaeopteris, lived around 350 million years ago. But Sharks? They laugh at trees. They've been around for 400 million years, skirting four global mass extinctions along the way.

It has been estimated that the bite force of great white shark is up to 4,000 PSI. For comparison, a tiger generates around 1,000 PSI of bite force.