More than 450 shark species have been documented as of 2014. Sharks have been around since prehistoric times, with evidence of their existence dating back hundreds of millions of years. The first sharks appeared in the world's oceans around 420 million years ago.
The longest shark is the 40-foot-long whale shark, while the smallest is the 8-inch-long dwarf lanternshark. Sharks can weigh as much as 11 tons. Most species have highly-developed senses of sight, hearing and smell and are able to detect prey from a far distance as well as see in deep ocean waters.
While most shark species live from 20 to 30 years, others live far longer. The whale shark has been documented to live to be more than 100 years old.