Researchers at Michigan State University have confirmed that the two-headed bull shark captured in March 2011 is really a two headed shark, and not a pair of conjoined twin sharks. Researchers ran a lot of tests including MRIs and X-rays. The two-headed baby shark was found by a fisherman inside the uterus of a bull shark.
The baby shark didn’t survive long after being removed from the mother, but the two-headed specimen generated quite a lot of attention, being the first example of dicephalia (two-headedness) seen in sharks. Apart from the two mouths, this one also had two stomachs and two hearts.