Although fancy caudae are important traits for chicken breeds, factors associated with their morphological diversity are not fully understood. We analyzed the caudal skeleton of the Tosa-jidori, Chabo, and Minohikichabo breeds with wild-type, erect, and rich caudae, respectively. Five of six Tosa-jidori chickens had four caudal vertebrae, whereas all six Chabo and five of six Minohikichabo chickens had five. The angle of the apex pygostyli with respect to the margo cranialis was significantly larger and smaller in Chabo and Minohikichabo than Tosa-jidori chickens, respectively. These findings indicated that the caudal skeleton is one of important factors for forming the characteristic traits of chicken breeds.
Keywords: bleached bone; computed tomography; fowl; pygostyle; tail feather.