Melanosome evolution indicates a key physiological shift within feathered dinosaurs
Melanosome evolution indicates a key physiological shift within feathered dinosaurs
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黑素体进化表明有羽毛恐龙的关键生理变化
DOI：
10.1038/nature12973
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发表时间：
2014-03-20
期刊：
影响因子：
64.8
通讯作者：
Shawkey, Matthew D.
中科院分区：
文献类型：
--
作者：
Li, Quanguo;Clarke, Julia A.;Shawkey, Matthew D.
已灭绝恐龙颜色图案的推断是基于含黑色素细胞器（黑素体）的形态与现存鸟类羽毛颜色之间的关系。这种关系相对于羽毛和其他新的外皮结构（例如已灭绝的祖龙的毛发和丝状身体覆盖物）的起源何时进化，尚未得到评估。在这里，我们从中国上侏罗统和下白垩统的 181 个现存羊膜动物类群和 13 个蜥蜴、海龟、恐龙和翼龙化石的体壁中取样。我们发现，在鸟类的谱系中，观察到的黑素体形态多样性的增加突然出现，接近手盗龙羽状羽毛的起源。同样，与所有变温羊膜动物相比，哺乳动物的黑素体形式多样性有所增加。在这两个进化枝中，哺乳动物和包括鸟类在内的手盗龙恐龙、黑素体的形式和颜色是相关的，并且颜色重建是可能的。相比之下，蜥蜴、海龟和鳄鱼皮肤以及祖龙类丝状身体覆盖物（恐龙“原羽毛”和翼龙“密纤维”）中的黑素体表现出有限的形式多样性，与现存分类单元的颜色无关。这些模式可以通过哺乳动物和鸟类的关键黑皮质素系统的趋同变化来解释，已知该系统会多效性地影响基于黑色素的着色和脊椎动物的新陈代谢率等能量过程，因此可能支持手盗龙恐龙的显着生理变化。
Inference of colour patterning in extinct dinosaurs,,has been based on the relationship between the morphology of melanin-containing organelles (melanosomes) and colour in extant bird feathers. When this relationship evolved relative to the origin of feathers and other novel integumentary structures, such as hair and filamentous body covering in extinct archosaurs, has not been evaluated. Here we sample melanosomes from the integument of 181 extant amniote taxa and 13 lizard, turtle, dinosaur and pterosaur fossils from the Upper-Jurassic and Lower-Cretaceous of China. We find that in the lineage leading to birds, the observed increase in the diversity of melanosome morphologies appears abruptly, near the origin of pinnate feathers in maniraptoran dinosaurs. Similarly, mammals show an increased diversity of melanosome form compared to all ectothermic amniotes. In these two clades, mammals and maniraptoran dinosaurs including birds, melanosome form and colour are linked and colour reconstruction may be possible. By contrast, melanosomes in lizard, turtle and crocodilian skin, as well as the archosaurian filamentous body coverings (dinosaur ‘protofeathers’ and pterosaur ‘pycnofibres’), show a limited diversity of form that is uncorrelated with colour in extant taxa. These patterns may be explained by convergent changes in the key melanocortin system of mammals and birds, which is known to affect pleiotropically both melanin-based colouration and energetic processes such as metabolic rate in vertebrates, and may therefore support a significant physiological shift in maniraptoran dinosaurs.