一项新的研究报告说，一个3500万年前的企鹅的羽毛化石披露了某些现代特质的线索。 在现代鸟类的羽毛中所发现的被称作黑色素体的色素颗粒在鸟羽化石中首次报导的时间是在2008年。

这些色素颗粒非常细小，人的毛发直径可容纳一百个黑色素体。 如今，Julia Clarke及其同事证明，化石化的黑色素体可确定企鹅的演化发展。 企鹅高度适应其寒冷的水生环境。 它们的翅膀和羽毛的变化使得它们能够快速地游泳（水中“飞行”）并保护它们在近乎冻结的水中不受伤害；然而，解释企鹅羽毛是如何演化的数据则非常少。 在本研究中，研究人员对一个在秘鲁发现的羽毛得到完好保存的3500万年前的企鹅进行了分析。 尽管远古企鹅的翅膀和羽毛的外观与当今企鹅的相似，但该研究团队发现，其羽毛中的黑色素体则与当今企鹅的并不一样。

明确地说，远古企鹅的色素细胞与许多其它水鸟的色素细胞类似，但却与当今企鹅的色素细胞不同。 这些结果提示，远古企鹅羽毛的形状和构成在影响诸如力量和水阻力等性质的微观变化之前就已经演化了，这也许对解释企鹅是如何及何时适应于水中生活的有所帮助。

英文摘要：

Science DOI: 10.1126/science.1193604

Fossil Evidence for Evolution of the Shape and Color of Penguin Feathers
Julia A. Clarke,1,* Daniel T. Ksepka,2,3 Rodolfo Salas-Gismondi,4 Ali J. Altamirano,4 Matthew D. Shawkey,5 Liliana D’Alba,5 Jakob Vinther,6 Thomas J. DeVries,7 Patrice Baby8,9

Penguin feathers are highly modified in form and function, but there have been no fossils to inform their evolution. A giant penguin with feathers was recovered from the late Eocene (~36 million years ago) of Peru. The fossil reveals that key feathering features including undifferentiated primary wing feathers and broad body contour feather shafts evolved early in the penguin lineage. Analyses of fossilized color-imparting melanosomes reveal that their dimensions were similar to those of nonpenguin avian taxa and that the feathering may have been predominantly gray and reddish-brown. By contrast, the dark black-brown color of extant penguin feathers is generated by strikingly large, ellipsoidal melanosomes previously unknown for birds. The nanostructure of penguin feathers was thus modified after earlier macrostructural modifications of feather shape linked to aquatic flight.

1 Department of Geological Sciences, University of Texas at Austin, Austin, TX 78712, USA.
2 Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695–8208, USA.
3 Department of Paleontology, North Carolina Museum of Natural Sciences, Raleigh, NC 27601–1029, USA.
4 Departamento de Paleontología de Vertebrados, Museo de Historia Natural-UNMSM, Lima 14, Perú.
5 Integrated Bioscience Program, University of Akron, Akron, OH 44325, USA.
6 Department of Geology and Geophysics, Yale University, New Haven, CT 06511, USA.
7 Burke Museum of Natural History and Culture, University of Washington, Seattle, WA 98195, USA.
8 IRD; LMTG; 14 Av. Edouard Belin, F-31400 Toulouse, France.
9 Université de Toulouse; UPS; LMTG; F-31400 Toulouse, France.