the two heads are joined directly to each other, but only one head has a functional torso{{px2mdash}}px2}}}}?in most cases, this manifests as an underdeveloped twin head joined to the head of a developed twin. Documented survival into childhood is extremely rare. Survival to adulthood is rare, but does occur in some forms of dicephalus parapagus dipus, as was reported in a case of dicephalic twin born at 36 weeks of gestation to a multigravida mother in central India.

There are many occurrences of multi-headed animals in mythology.