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.
Read more on the NSRRC website
Image: Mummified fossil of the early Permian reptile Captorhinus