An equine fetal monster dicephalus tetrapus dibrachius.

Double monsters are structurally related to monozygotic twins and the reported frequency of these abnormalities in the equine species is low. Symmetrical, double development in both the cephalic region and caudal trunk was demonstrated along with a common undeveloped cervical mass. Anomalies found in the separate genito-urinary systems added another variant to this case.