Fig. 1

Feature of horn bud and frontal skin from horned and polled yak fetuses. a Macroscopic picture of a horn bud from a horned fetus. Black arrow indicates the area of indented skin. b Macroscopic picture of a polled fetus without indentation of the horn bud. c Histological section of a horn bud with multiple layers of vacuolated keratinocytes. Black star indicates the presence of clusters of dermal cells displaying different tissue. d Histological section of the “horn bud” region in polled yak fetus. e Histological section of frontal skin in horned yak fetus. Ep = epidermis, de = dermis, hf = hair follicles. The images in panels c, d and e were taken at 100 × magnification