Breathing and moving in the ancient world of reptiles: What a mummified 289-million-year-old reptile can reveal about us today

A 289-million-year-old mummified reptile is providing scientists with a window into how bodies have evolved when it comes to breathing and movement. Published in Nature on April 8, 2026, the study introduces the oldest known mummified remains of a terrestrial vertebrate — a small early Permian reptile called Captorhinus — preserved with its skin, native proteins, and the cartilage framework of its entire respiratory system still intact. The finding predates previous evidence of preserved biological proteins in fossils by nearly 100 million years.

“This is an exciting discovery in paleontology with great evolutionary significance,” says University of Toronto Mississauga researcher and lead author Robert Reisz. “This unprecedented preservation of a respiratory system showcases the oldest known complete rib cage for muscle powered inhalation and exhalation.”

The mummified reptile was likely preserved because it died in a cave system, became encased in fine clay, and was saturated with hydrocarbons from an oil seep, a rare combination that protected delicate soft tissues across geological time. Because the remains were very fragile, the research team skipped traditional fossil preparation techniques entirely and co-authors Joseph Bevitt and Ethan Mooney used neutron computed tomography (CT) scanning and imaging, and researchers from three different centers used geochemical techniques — including X-ray fluorescence (XRF), electron probe microanalysis (EPMA), and synchrotron radiation Fourier-transform infrared spectroscopy (SR-FTIR) — to image and analyze the specimens. Co-author Tea Maho from the University of Toronto Mississauga also conducted histological sampling that indicated the cartilages are calcified as in living lizards, and the chemical analyses confirmed this interpretation.

“We propose that this system found in Captorhinus represents the ancestral condition for the kind of rib-assisted respiration present in living reptiles, birds, and mammals. This efficient respiratory apparatus is important for their more active, energetic, and competitive lifestyles compared to their amphibian counterparts,” said Reisz.

Equally striking is evidence that the shoulder girdle shows that there was likely movement on each side during locomotion, a feature seen in many living lizards and now confirmed as an ancient trait rather than a later evolutionary innovation.

“The mummified Captorhinus is among the most significant early amniote fossils in the world,” added Mooney. “It has offered an unparalleled window into the appearance, lifestyles, and evolution of the earliest reptiles, expanding dramatically our understanding of this pivotal episode of amniote evolution. As more work continues on this time period, more incredible discoveries are sure to be unearthed.”