We recently wrote about a two-headed bull shark found by fishermen. One of our readers, Christopher Johnston, then sent us an email with photos he had taken on September 27, 2008 of a similarly surprising find: a two-headed blue shark. As far as we know these photos have never been published anywhere before.
As we previously reported, there have been only about a half dozen reported cases of two-headed sharks. The phenomenon arises through conjoined development of twins, the same process that produces what used to be called Siamese twins in people.
Source: National Geographic