SEE: Two-headed deer discovered in first documented case of conjoined white-tailed deer twins

In May 2016, a man on a mushroom-hunting trip came across two dead fawns. They were conjoined from the neck down, so the deer had two heads but one body.

He contacted the Minnesota Department of Natural Resources, where the animals were frozen until scientists could take an in-depth look at them.

Researchers from the University of Minnesota and the University of Georgia conducted the study, published in The American Midland Naturalist journal, and drew some interesting conclusions.

After unthawing the deer, they performed CT and MRI scans and a necropsy, or animal autopsy. They realized the fawns had never breathed air, which means they were stillborns. They also shared several body parts, but had two hearts and two intestinal tracts. They had normal fur, heads and legs, and "almost perfect" spot patterns running up their necks.

The biologists believe the deer are the first of their kind to reach full term and be delivered by the mother. In other cases, the conjoined twin fawns did not live past the utero stage.

"It's amazing and extremely rare," UGA researcher Gino D'Angelo said in a statement. "We can't even estimate the rarity of this. Of the tens of millions of fawns born annually in the U.S., there are probably abnormalities happening in the wild we don't even know about."

They are still unsure how the twins became conjoined. “Even in humans we don’t know,” D’Angelo said. “We think it’s an unnatural splitting of cells during early embryo development.”

The conjoined deer, which were turned into taxidermy, will be on display at the Minnesota Department of Natural Resource's headquarters and a skeletal display will be located at the University of Minnesota Veterinary Anatomy Museum.