Morphology of a dicephalic cat.

A detailed anatomical study of a dicephalic iniodymic monosomic cat in conjunction with the morphogenetical implications of the observed anomalies is presented. The animal exhibited two heads joined at the level of an anomalous medial exoccipital bone. Two brains and two foramina magna were present. The vertebral column was single but the cranial cervical vertebrae (C2 to C5) had doubled bodies. Cervical rachischisis with myeloschisis were associated defects. Two nasopharyngeal and oropharyngeal cavities converged caudally into a single laryngopharynx. The esophagus, larynx and trachea were single. Duplication of the tongue and hyoid apparatus was present. Palatoschisis affected both oral cavities. Hypoplasia of the anatomical structures in the medial aspects of both heads was observed. Microphthalmia was also observed in both medial eyes. Comparative aspects of the morphology, causative agents, and mechanisms and anomalous morphogenesis of anterior duplications are reviewed and discussed.