Dipygus

Dipygus is a severe congenital deformity where the body axis forks left and right partway along the torso with the posterior end (pelvis and legs) duplicated. Dipygus is a severe congenital deformity where the body axis forks left and right partway along the torso with the posterior end (pelvis and legs) duplicated. Myrtle Corbin was a dipygus; she married and had five children. In human cases, the inner two of the four hindquarters develop much smaller than normal. This is a type of 'teras catadidymum' ('monster twinned below'). Another sort of deformity with extra legs can happen from a degenerated conjoined twin, as may have happened with Frank Lentini with his third leg.