289-million-year-old mummy fossil presents earliest evidence of rib-based breathing

Paleontologists described a 289-million-year-old mummified Captorhinus aguti fossil from Richards Spur, Oklahoma.

Neutron CT revealed preserved skin, cartilage and a segmented breastbone with ribs anchored to the shoulder.

The specimen shows the oldest known evidence of costal aspiration and rib-powered inhalation.

Authors propose this rib-based system is ancestral for modern amniotes.