A cat with two faces, two mouths, two noses and three blue eyes called Frank and Louie has died.
The cat made it into the 2012 Guinness World Records as the oldest surviving Janus cat, named after the Roman god with two heads.
Owner Martha Stevens of Worcester said that Frank and Louie passed away at the Cummings School of Veterinary Medicine at Tuft's University in Grafton on Thursday.
Stevens was told by vets at the clinic that the Janus cat was suffering from a "really bad cancer" and then put to sleep.
Frank and Louie's owner was initially told that the cat would only survive a few days, although Stevens was determined to keep him alive as long as possible.
"But the next day I came in with him [to the clinic], and the next day, and we started thinking he was going to survive," she told The Telegram of Worcester. "I tube fed him until he was 3 months old, because I was afraid he wouldn't be able to eat."
Janus kittens often have cleft palates or other deformities that make it difficult for them to get nourishment and they are also rejected by their mothers.
Domestic cats with two faces are extremely rare, says Leslie Lyons of the University of Missouri's Department of Veterinary Medicine and Surgery, who specializes in feline genetics.
"Janus cats occur when one embryo either splits to form twins, or two embryos early in development don't quite properly fuse together," Lyons told the National Geographic.
"We know there's a variety of genetic mechanisms that could cause it, though only DNA testing could pinpoint the exact cause.
"It's very nice that there are individuals in our society that have this type of compassion," added Lyons. "Like taking care of a handicapped child, they've taken care of a [special-needs] cat for 15 years."
Two-faced animals aren't limited to cats, as there are examples in most mammals, vertebrates and marsupials.