Chinese Academy of Sciences Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing 210008, China;
Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695.
Proc Natl Acad Sci U S A. 2019 Feb 19;116(8):3018-3023. doi: 10.1073/pnas.1815703116. Epub 2019 Jan 28.
Dinosaur fossils possessing integumentary appendages of various morphologies, interpreted as feathers, have greatly enhanced our understanding of the evolutionary link between birds and dinosaurs, as well as the origins of feathers and avian flight. In extant birds, the unique expression and amino acid composition of proteins in mature feathers have been shown to determine their biomechanical properties, such as hardness, resilience, and plasticity. Here, we provide molecular and ultrastructural evidence that the pennaceous feathers of the Jurassic nonavian dinosaur were composed of both feather β-keratins and α-keratins. This is significant, because mature feathers in extant birds are dominated by β-keratins, particularly in the barbs and barbules forming the vane. We confirm here that feathers were modified at both molecular and morphological levels to obtain the biomechanical properties for flight during the dinosaur-bird transition, and we show that the patterns and timing of adaptive change at the molecular level can be directly addressed in exceptionally preserved fossils in deep time.
恐龙化石具有各种形态的表皮附属物，被解释为羽毛，这极大地增进了我们对鸟类和恐龙之间进化联系的理解，以及羽毛和鸟类飞行的起源。在现生鸟类中，成熟羽毛中蛋白质的独特表达和氨基酸组成被证明决定了它们的生物力学特性，如硬度、弹性和塑性。在这里，我们提供了分子和超微结构证据，证明侏罗纪非鸟恐龙的羽片由羽β-角蛋白和α-角蛋白组成。这很重要，因为现生鸟类的成熟羽毛主要由β-角蛋白组成，特别是在形成翼的羽枝和羽小枝的羽轴中。我们在这里证实，羽毛在分子和形态水平上都经过了修饰，以获得恐龙-鸟类过渡时期飞行所需的生物力学特性，并且我们表明，在深层时间的保存极好的化石中，可以直接研究分子水平上适应性变化的模式和时间。
