A fisherman found a two-headed bull shark in the Gulf of Mexico off the coast of Florida in 2011, marking the first discovery of conjoined twin bull sharks.
The discovery was documented in the Journal of Fish Biology and explained how after conducting X-ray testing on the specimen, researchers determined that there were two developed heads contained in the fetus-an anomaly known as dicephalia, where one fetus has two heads.
And the fetus was reportedly still alive inside the mother when the fisherman discovered it, along with several other fetuses.
The study's authors attempted to determine whether environmental pollution contributed to the mutation.
"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," the authors wrote.
"Assigning the observation of a single deformed specimen to that cause, especially when considering the presence of additional fetuses in the mother with apparently normal anatomy was noted by the fisherman, however, is not warranted by any information developed here."
The fisherman apparently removed the shark fetuses from the mother at the expense of her life and found the two-headed specimen. But when the babies were cut from the umbilical cord, the two-headed fetus quickly died while the others were released into the wild.
And while two-headed sharks have been observed in species like the dogfish shark, ilk shark and blue shark, this is the first time one has been discovered in a bull shark.
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