10-year-old two-headed tortoise Janus, named after the the Roman two-faced god of gates, meets crowds at the Natural History Museum in Geneva on his birthday.
Polycephaly is the condition of having more than one head. A variation is an animal born with two faces on a single head, a condition known as diprosopus.
In human beings such conjoined twining is commonly called dicephaly. Interestingly, conjoined animals are generally regarded as being one creature, while conjoined twins like the Tocci Brothers are generally perceived as two separate individuals fused together.