“…Reptilia are the only animal class belonging to both ectotherms and amniotes, and Aves are evolved from reptiles by one order. P450 aromatase is expressed in the granulosa cell layer of most mammalian species, such as humans [14], mice, rats [15], and brushtail possums [16], although in the ovary of pigs, it was expressed in not only the granulosa cell layer but also the theca cell layer [17], and in that of the tree shrew, it was expressed only in the thecal cell layer [18]. Unlike most mammalian species, P450 aromatase is expressed in the thecal cell layer of the chicken ovary [19].…”