The photo above is of a two-headed bull shark. The first ever found. Creepy  right?

Actually, it’s pretty cool. The find was just published in the  Journal of Fish Biology. A fisherman found the fetus in the Gulf of Mexico,  off the coast of Florida in April 2011. It has two well-developed heads, the  researchers discovered after putting it through an X-ray.

This anomaly is called dicephalia. These aren’t conjoined twin sharks — it’s  genetically one shark that has grown two heads. When the shark was discovered,  it was still alive in its mother, with several other live fetuses.

From the paper, it seems like the fisherman sacrificed the mother and removed  the baby sharks, finding this two-headed one. The report says that it quickly  died when the umbilical cord was cut. Its siblings survived and were released  into the wild.

This two-headed trait has been found in other shark species, including the  dogfish shark, ilk shark, and blue shark, among others. This is the first time  they’ve found it in the Bull Shark though.

The mutation could have been caused by environmental pollution, the authors  note in the paper:

This latter explanation is tempting given the  increasing number of reports of anatomical and physiological deformities in  fishes exposed to pollution emitted from the Deepwater Horizon oil spill that  took place from 20 April until 15 July 2010.

Assigning the observation of a single deformed  specimen to that cause, especially when considering the presence of additional  foetuses in the mother with apparently normal anatomy was noted by the  fisherman, however, is not warranted by any information developed here.

Here’s what the X-rays look like:

two headed shark fetus x rays

Wagner, et. al, Journal of Fish Biology, 2013