Piglet with<unk>  at Ukrainian National Chernobyl Museum in Kyiv<unk>  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<unk> ; 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.
Dipygus
Tophus
Ipas 
Pectus
Maxilla
Pterygium
Pterygium 
Theriac