These feathers, then, presumably adorned a diving bird-perhaps Hesperornis, a flightless North American diver from precisely this period.

这些羽毛想必当时归潜鸟所有——也许“黄昏鸟”，一种恰好生活在这一时期北美潜鸟。

And the other was Hesperornis, which resembled a huge, flightless loon.

另一个黄昏鸟，它看起来像一只巨大潜鸟。

But both it and Hesperornis also had teeth, like most non-avian theropods did.

但始祖鸟和黄昏鸟也有牙齿，就像大多数非鸟类兽脚亚目恐龙一样。

Hesperornis and Ichthyornis were soon classified as ornithurines, a group of Mesozoic birds whose names means " bird tail." These ancient birds had short tails, instead of the longer bony tail of Archaeopteryx.

黄昏鸟和鱼鸟很快被归类为鸟尾类，这一群中生代鸟类， 其名称意思“鸟尾” 。 这些远古鸟类拥有短尾巴，而始祖鸟那样长骨质尾巴。

So it was clear to scientists that these " opposite birds" belonged to a different lineage than the likes of Hesperornis, Ichthyornis, and the other ornithurines.

因此，科学家们很清楚这些“反鸟类”属于一个与黄昏鸟、鱼鸟和其他鸟尾类同谱系。