'Janus Cat' Born in China: How Can an Animal Have 2 Faces?

A "Janus cat," born with two faces, meows from two mouths in a new video from Chongqing, China.

The cat, according to Newsflare, died at 2 days old. A short life span is common for these two-faced cats, which have a condition called diprosopus. The name "Janus" refers to the similarly two-faced Roman god.

Occasionally, diprosopus is caused by a case of conjoined twinning in which just one head forms, said Niels Pedersen, a professor emeritus at the UC Davis School of Veterinary Medicine. More often, Pedersen told Live Science, the problem is a hiccup in a gene that makes a protein named "sonic hedgehog." The protein is important in the embryonic development of the skull and face, as well as the extremities. It's named after the video game hedgehog for quirky reasons: Previously discovered, related proteins, had been named after different species of hedgehogs because of their spiky shapes. The discovery of the sonic hedgehog gene happened just around the time the Sega game hit the U.S. (The researcher who named it had kids who were aficionados.) [The 12 Weirdest Animal Discoveries]

Mutations in the sonic hedgehog gene are partially responsible for the loss of limbs in snakes, for example, and changes in the gene have been implicated in the evolutionary divergence between species.

In diprosopus, the sonic hedgehog protein is overexpressed, meaning the body makes too much of it. (Other genetic mutations might cause diprosopus, too, feline geneticist Leslie Lyons told National Geographic in 2014; it would take genetic testing to prove the culprit.) Diprosopus can happen in animals other than cats, with reported cases including pigs and chicks. In humans, diprosopus is incredibly rare, with one 2014 case report in the Journal of South Asian Federation of Obstetrics and Gynecology pegging the rate at between 1 in 180,000 and 1 in 15 million births. At the time it was published, that paper — which reported on the stillbirth of a 26-week-old fetus with two complete faces — there had been only 35 previous cases reported in the medical literature. Most fetuses with diprosopus develop other anatomical problems, according to that case study. In the 2014 case, the fetus also had anencephaly, meaning that the brain and skull were underdeveloped.

Only a few human infants with diprosopus have survived past birth, the researchers wrote. The longest-living child with the condition, Lali Singh, was born in 2008 in Delhi and survived for two months. In 2014, a set of conjoined twins named Faith and Hope Howie were born in Australia with one head, two faces and two brains, each joined to a single brain stem and body. The babies lived for 19 days.

Like the unfortunate kitten in China, most animals with diprosopus are either stillborn or can't survive long outside the womb. The most famous exception was Frank and Louie, a Janus cat that lived a remarkable 15 years. Frank and Louie died of cancer in 2014, two years after claiming a Guinness World Record as the world's oldest Janus cat.

Original article on Live Science.

Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz.