de Boer L E
Nature. 1980 Sep 4;287(5777):84-5. doi: 10.1038/287084a0.
The extensive literature on the origin of the ratites focuses mainly on three questions: are the ratites mono- or polyphyletic, did they evolve from flying ancestors, and are they primitive or advanced? Opinion tends to accept a common descent from flying ancestors for the large ratites (for a summary of ideas see ref. 1). They would have evolved on Gondwanaland some time in the Cretaceous and have become dispersed over the southern continents after its fragmentation. However, the position of the small New Zealand kiwis, in many respects the most pecular of all birds, is still a matter for conjecture. The chromosome complements of the large ratites have been found to be remarkably uniform. The chromosome set of the kiwi, described here, clearly links up with these, which may be recorded as another indication for monophyly of all ratites. It also indicates that we are dealing here with very ancient karyotypes.
平胸鸟是单系起源还是多系起源，它们是否从会飞的祖先进化而来，以及它们是原始的还是进化的？对于大型平胸鸟，人们倾向于接受它们起源于会飞的祖先（有关观点总结见参考文献1）。它们可能在白垩纪的某个时期在冈瓦纳大陆上进化，并在冈瓦纳大陆分裂后散布到南半球各大陆。然而，小型的新西兰几维鸟在许多方面是所有鸟类中最特殊的，其情况仍然是一个推测的问题。已发现大型平胸鸟的染色体组非常一致。这里描述的几维鸟的染色体组显然与这些染色体组相关联，这可以被视为所有平胸鸟单系起源的另一个证据。这也表明我们在这里处理的是非常古老的核型。
