Carr J L, Bickham J W
Cytogenet Cell Genet. 1981;31(3):178-83. doi: 10.1159/000131644.
A heteromorphism in a pair of macrochromosomes in male Siebenrockiella crassicollis is interpreted as an XX/XY sex determining system. The heteromorphism involves a difference in centromere position and amount and distribution of heterochromatin. The only other sex chromosome system known in turtles is found in the kinosternid genus Staurotypus and is also an XX/XY system, but it involves a different chromosome pair and different chromosomal rearrangements. These two systems have independently arisen within the suborder Cryptodira and share no common ancestry. The sex chromosome system in Siebenrockiella represents a relatively early stage of differentiation. It differs from the hypothesized steps of differentiation in having a heterochromatically derived X.
雄性粗颈龟一对大染色体中的异形性被解释为XX/XY性别决定系统。这种异形性涉及着丝粒位置以及异染色质数量和分布的差异。龟类中已知的唯一其他性染色体系统存在于动胸龟科的动胸龟属中，也是XX/XY系统，但涉及不同的染色体对和不同的染色体重排。这两个系统在侧颈龟亚目内独立出现，没有共同的祖先。粗颈龟的性染色体系统代表了分化的相对早期阶段。它与假设的分化步骤的不同之处在于有一个由异染色质衍生而来的X染色体。
