Sites J W, Bickham J W, Haiduk M W
Science. 1979 Dec 21;206(4425):1410-2. doi: 10.1126/science.92052.
C-banding, G-banding, and silver (Ag-AS) staining techniques reveal a distinctive sex chromosome system in the turtle Staurotypus salvinii. Unlike previously described systems in most other vertebrate groups in which the Y or W is derived and the homogametic sex represents the primitive condition, the reverse is true for S. salvinii. The X chromosome is derived; thus the homogametic sex (female) is more derived than the heterogametic sex. The male is intermediate between the female and the ancestral condition observed in other turtle species. Staurotypus does not confirm to the general model of sex chromosome evolution for diploid dioecious organisms.
C带、G带和银染（Ag-AS）技术揭示了萨尔文氏蟾龟（Staurotypus salvinii）独特的性染色体系统。与大多数其他脊椎动物类群中先前描述的系统不同，在那些系统中Y或W染色体是衍生而来的，同配性别代表原始状态，而萨尔文氏蟾龟的情况则相反。X染色体是衍生而来的；因此，同配性别（雌性）比异配性别更为衍生。雄性处于雌性和其他龟类物种所观察到的祖先状态之间。萨尔文氏蟾龟不符合二倍体雌雄异体生物性染色体进化的一般模式。
