A two-headed bull shark foetus has been found by fishermen in the Gulf of Mexico.
The specimen is the first recorded incidence of the condition, known as axial bifurcation, in a bull shark or Carcharhinus leucas.
The find was published in the Journal of Fish Biology.
It noted: “External examination, Radiography and magnetic resonance imaging revealed a case of monosomic dicephalia where the axial skeleton and internal organs were found to divide into parallel systems anterior to the pectoral girdle resulting in two well-developed heads.”
Michael Wagner, a study co-author and researcher at Michigan State University said the deformity is the result of an embryo beginning to split into twins, but doing so incompletely.
The foetus was live when it was found, but probably wouldn’t have lived for very long in the wild, Wagner told OurAmazingPlanet.
He said: "When you're a predator that needs to move fast to catch other fast-moving fish … that'd be nearly impossible with this mutation."
A further reason the shark wouldn’t have lived long is its small body.
Wagner added: “It had two very developed heads, but a very stunted body.”