Experts say the baby beast, found in the Gulf of Mexico, was a single shark rather than conjoined twins.
Boffins at Michigan State University carried out a study on the strange creature.
"This is certainly one of those interesting and rarely detected phenomena,” said Michael Wagner, the university’s assistant professor of fisheries and wildlife.
“It’s good that we have this documented as part of the world’s natural history.”Wagner and his team used MRIs to reveal the shark had two distinct heads, hearts and stomachs, with the remainder of the body joining together at the back to form a single tail.
The team could not give a reason for the strange anomaly but said they would have to find other similar sharks in order to investigate.
The two-headed bull shark found last year after a fisherman cut into the uterus of adult shark and discovered the baby.
It was brought to the marine science department at Florida Keys Community College and then taken to the Michigan University for further analysis.
It is thought similar creatures may have died before being born.
“You’ll see many more cases of two-headed lizards and snakes,” said Prof Wagner. “That’s because those organisms are often bred in captivity, and the breeders are more likely to observe the anomalies.”
The case was publicised in the Journal of Fish Biology.
