Every so often, a sensational animal story featuring a "Janus cat" will go viral. Most recently it was the tale of "Frank and Louie" who entered the 2012 Guinness Book of World Records as the longest-surviving Janus cat. So who exactly is a Janus cat and what makes them so special?

In simple terms, a Janus cat is a cat with two faces. In these cases, the cat suffers from Diprosopus, "an extremely rare congenital disorder whereby part or all of the face is duplicated on the head." It's not a conjoined twins situation caused by the incomplete separation of two embryos, rather it means the cat has too much of a protein called sonic hedgehog homolog (SHH), which makes facial features wider and in severe cases, leads to the duplication of facial structures.

Frank and Louie:

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Why Are They Called Janus Cats?

The origin of the name comes from the Roman god, Janus. In ancient Roman religion and mythology, Janus is the god of beginnings and transitions, whose two faces look to the future and the past. His image is often used on gates, doors, doorways, and the month of January is named for him.



How Long Do They Live?

Most Janus cats and other two-faced animals don't love long due to associated internal organ abnormalities and brain abnormalities. Frank and Louie are of course the exception, having set the record at 12-years-old.