It's not known why the twins were conjoined.
There have been two other conjoined white-tailed deer fawns cases reported in the past, however neither made it through the full pregnancy, the Daily Mail reported.
The discovery of a two-headed mutant fawn in a Minnesota forest has become a landmark in the study of wildlife deformity. According to study co-author Gino D'Angelo, a researcher at the University of Georgia, lab tests including a CT scan and MRI, revealed the fawns had two separate head-neck regions which re-joined along the spine.
The hunter immediately alerted the Minnesota Department of Natural Resources, and the fawns were consequently frozen until a necropsy could be conducted.
The discovery was made in May 2016, when a mushroom hunter came across the twins about a mile from the Mississippi River in Freeburg, Minn., located in the southeast portion of the state. There were two heads, but one body.
"It's fantastic and extremely rare", D'Angelo said in the release. "Of the tens of millions of fawns born annually in the USA, there are probably abnormalities happening in the wild we don't even know about", D'Angelo said in a press statement.
The animals appeared to be recently deceased and were clean and dry, according to Gino D'Angelo, a University of Georgia researcher who studied the deer.
Treasury yields surge pushes Wall Street lower
Stocks are opening moderately higher on Wall Street, led by gains in technology, health care and energy companies. The S&P 500 lost 19 points, or 0.68%, to 2,711 and the Nasdaq Composite fell 60 points, or 0.81%, to 7,352.
They had two hearts, which shared a pericardial sac - the outer layer of a heart.
"Animals that are stillborn, they don't last long on the landscape because of scavengers", added Cornicelli.
Researchers were only able to find 19 confirmed instances of conjoined twins in wildlife between 1671 and 2006, five of them were within the deer family.
The two-headed deer found in Minnesota is an extremely rare specimen not only among its species but also among other species.
"Their anatomy indicates the fawns would never have been viable", D'Angelo told The Independent. However, they had been discovered dressed and at a natural place, suggesting the doe attempted to take care of them following delivery. "The maternal instinct is very strong".
For their new study, D'Angelo and his colleagues conducted computed tomography (CT) and magnetic resonance imaging (MRI) scans on the conjoined twins, then conducted a full necropsy. "The taxidermists, Robert Utne and Jessica Brooks, did a great job with the mount and treated it very respectfully".