一组恐龙化石提示，羽毛和翼翅样结构首先是为了求偶而演化出的。大多数已知的羽毛得到良好保存的恐龙化石来自中国，但现在由Darla Zelenitsky及其同事所描述的化石则来自加拿大的阿尔伯塔。研究人员分析了3具来自鸵鸟样恐龙物种埃德蒙顿似鸟龙的骨架——2具幼年的和1具成年的骨架。所有3个样品看来都覆盖有短的、绒毛样的羽毛，但只有该成年的样品显示了长羽的证据——在其前肢上有着硬的中心轴。长羽毛的延迟发育提示这些羽毛只是当这些动物在达到性成熟时才会使用，也许用其来求偶、炫耀或育雏。文章的作者提示，羽毛只是在后来才添加了诸如体温调节或飞行等其它的用途。（生物谷Bioon.com）
doi: 10.1126/science.1225376
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Feathered Non-Avian Dinosaurs from North America Provide Insight into Wing Origins
Darla K. Zelenitsky, Francois Therrien, Gregory M. Erickson, Christopher L. DeBuhr, Yoshitsugu Kobayashi, David A. Eberth, and Frank Hadfield
Previously described feathered dinosaurs reveal a fascinating record of feather evolution, although substantial phylogenetic gaps remain. Here we report the occurrence of feathers in ornithomimosaurs, a clade of non-maniraptoran theropods for which fossilized feathers were previously unknown. The Ornithomimus specimens, recovered from Upper Cretaceous deposits of Alberta, Canada, provide new insights into dinosaur plumage and the origin of the avian wing. Individuals from different growth stages reveal the presence of a filamentous feather covering throughout life and winglike structures on the forelimbs of adults. The appearance of winglike structures in older animals indicates that they may have evolved in association with reproductive behaviors. These specimens show that primordial wings originated earlier than previously thought, among non-maniraptoran theropods.
