Pan Yanhong, Qi Zeming, Hu Jianfang, Zheng Xiaoting, Wang Xiaoli
State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Centre for Research and Education on Biological Evolution and Environment, Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing 210023, China.
National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230027, China.
PNAS Nexus. 2024 Aug 21;3(9):pgae341. doi: 10.1093/pnasnexus/pgae341. eCollection 2024 Sep.
Exceptionally preserved feathers from the Mesozoic era have provided valuable insights into the early evolution of feathers and enabled color reconstruction of extinct dinosaurs, including early birds. Mounting chemical evidence for the two key components of feathers-keratins and melanins-in fossil feathers has demonstrated that exceptional preservation can be traced down to the molecular level. However, the chemical changes that keratin and eumelanin undergo during fossilization are still not fully understood, introducing uncertainty in the identification of these two molecules in fossil feathers. To address this issue, we need to examine their taphonomic process. In this study, we analyzed the structural and chemical composition of fossil feathers from the Jehol Biota and compared them with the structural and chemical changes observed in modern feathers during the process of biodegradation and thermal degradation, as well as the structural and chemical characteristics of a Cenozoic fossil feather. Our results suggest that the taphonomic process of feathers from the Cretaceous Jehol Biota is mainly controlled by the process of thermal degradation. The Cretaceous fossil feathers studied exhibited minimal keratin preservation but retained strong melanin signals, attributed to melanin's higher thermal stability. Low-maturity carbonaceous fossils can indeed preserve biosignals, especially signals from molecules with high resistance to thermal degradation. These findings provide clues about the preservation potential of keratin and melanin, and serve as a reference for searching for those two biomolecules in different geological periods and environments.
中生代保存异常完好的羽毛为羽毛的早期演化提供了宝贵见解，并使包括早期鸟类在内的已灭绝恐龙的颜色得以重建。化石羽毛中羽毛的两种关键成分——角蛋白和黑色素——越来越多的化学证据表明，异常保存可以追溯到分子层面。然而，角蛋白和真黑色素在石化过程中所经历的化学变化仍未完全了解，这给化石羽毛中这两种分子的鉴定带来了不确定性。为了解决这个问题，我们需要研究它们的埋藏过程。在这项研究中，我们分析了热河生物群化石羽毛的结构和化学成分，并将其与现代羽毛在生物降解和热降解过程中观察到的结构和化学变化，以及新生代化石羽毛的结构和化学特征进行了比较。我们的结果表明，白垩纪热河生物群羽毛的埋藏过程主要受热降解过程控制。所研究的白垩纪化石羽毛角蛋白保存极少，但黑色素信号强烈，这归因于黑色素较高的热稳定性。低成熟度的碳质化石确实可以保存生物信号，尤其是来自对热降解具有高抗性分子的信号。这些发现为角蛋白和黑色素的保存潜力提供了线索，并为在不同地质时期和环境中寻找这两种生物分子提供了参考。
