While fishing off the coast of the Florida Keys, a man found a 2-headed shark fetus. The fisherman kept the 2-headed live bull shark fetus and then turned it over to scientists.

The scientists studied the 2 headed shark fetus and published their findings in The Journal Of Fish Biology. There are only 6 recorded findings of 2 headed sharks. This is the first time this mutation has been seen in a bull shark.

The scientific term for a 2 headed shark (or anything else) is axial bifurcation. This is the process in which the embryo begins to split into two different organisms, like twins. With axial bifurcation, the embryo does not split completely and forms the 2 headed mutation.

Michael Wagner is a researcher at Michigan State University and a co-author on the study. He told Live Science, "The two headed fetus likely would not have lived for very long in the wild. When you're a predator that needs to move fast to catch other fast moving fish...that'd be nearly impossible with this mutation."

Wagner says that this mutation occurs in a variety of different animals, including humans. Wagner says the 2 headed shark will help researchers to understand the mutation better, including how it comes to be.

Wagner says another reason the 2 headed shark fetus would not have survived long is due to its size.

"It had very developed heads, but a very stunted body. There is only so much energy that can go into the body's development and it went into the shark's double noggins," Wagner told Live Science.

Bull Sharks are considered by experts to be the most dangerous shark in the world. They are highly aggressive and can live in salt or fresh water. They usually live near areas with a large population, such as tropical shore lines.

According to National Geographic the Bull Shark is one of three sharks most likely to attack humans; tiger sharks and great white sharks are the other two.  

A wild Bull shark can live up to 16 years and grow up to 11 feet long, weighing anywhere from 200 to 500lbs.