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289-Million-Year-Old “Reptile Mummy” Unearthed: NSRRC and Global Team Reveal the Evolution of Breathing
2026/05/19
Neutron Computed Tomography
Mummified fossil of the early Permian reptile Captorhinus
Synchrotron radiation-based micro-ATR-FTIR spectroscopy
Synchrotron radiation-based micro-ATR-FTIR spectroscopy

An international collaborative research team composed of the National Synchrotron Radiation Research Center (NSRRC), University of Toronto, Harvard University, the Australian Centre for Neutron Scattering, and Jilin University has achieved a breakthrough in vertebrate paleontology and evolutionary biology. The team successfully characterized a mummified fossil of the early Permian reptile Captorhinus, dating back approximately 289 million years. The discovery not only provides critical insights into the evolution of the respiratory system in early amniotes but also establishes a new record for the oldest known preservation of soft tissues and protein-related molecular signatures. The findings were published in Nature on April 8.

Captorhinus resembled a small lizard and predates dinosaurs by nearly 40 million years. The exceptionally preserved fossil was excavated from the Richards Spur cave system in Oklahoma, USA. Unique geological conditions at the site, including hydrocarbon-rich petroleum seepage and oxygen-poor, muddy sediments, effectively inhibited microbial decomposition, enabling the specimen to be preserved in a near-mummified state. As a result, delicate soft tissues, including skin, cartilage, and thoracic structures, were retained with extraordinary fidelity. To investigate this rare specimen, the research team integrated morphology, molecular analysis, and synchrotron-based techniques into a comprehensive multiscale study of vertebrate evolution.

 Unlike amphibians, which primarily rely on cutaneous and buccal pumping for respiration, amniotes — including humans and all terrestrial vertebrates — evolved a rib-based ventilatory system capable of far more efficient oxygen exchange. This rib-driven breathing mechanism represented a major evolutionary innovation, enabling vertebrates to adapt to terrestrial environments and ultimately laying the foundation for the extensive diversification and ecological dominance of amniotes on land.

 Using high-resolution Neutron Computed Tomography, the international research team performed non-destructive three-dimensional reconstruction of the fossil and, for the first time, clearly visualized the complete respiratory architecture of Captorhinus. The reconstructed anatomy revealed the integrated relationships among the cartilaginous sternum, sternal ribs, elongated rib structures, and the shoulder girdle. These findings demonstrate that Captorhinus had already evolved the ability to ventilate its thoracic cavity through rib expansion, representing an early form of costal aspiration breathing.
  
 In parallel, the NSRRC research team employed synchrotron radiation-based micro-ATR-FTIR spectroscopy (SR-µATR-FTIR) at the Taiwan Light Source to conduct molecular-level analyses of fossilized bone, cartilage, and skin tissues. The technique successfully detected protein structure-related spectral signatures at the micrometer scale. Because paleomolecular signals are typically extremely weak and difficult to resolve using conventional infrared sources, the high brilliance and superior signal-to-noise characteristics of synchrotron infrared radiation were essential for identifying molecular traces preserved within the fossil. The results indicate that this specimen still retains molecular signatures associated with proteinaceous structures, establishing the oldest known record of preserved soft tissues and protein-related molecular remnants in a terrestrial vertebrate fossil — extending the previous record by nearly 100 million years. These findings provide important new insights into the mechanisms governing long-term preservation of ancient soft tissues.

Dr. Yao-Chang Lee noted that this study not only provides new scientific perspectives on the evolution of respiratory systems in early amniotes but also highlights the importance of cross-scale analytical approaches in paleontological research. By integrating neutron computed tomography with synchrotron infrared microspectroscopy, the research team performed complementary analyses spanning three-dimensional morphology and molecular composition. This combined approach enabled reconstruction of the fossil thoracic architecture and its potential respiratory mechanism, while simultaneously revealing preserved chemical and molecular information within the specimen. Together, these methods establish an integrated evidence framework linking morphology to molecular signatures, thereby reconstructing critical details of biological evolution and physiological function from nearly 300 million years ago.

https://www.nature.com/articles/s41586-026-10307-y