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289-Myr Captorhinus Fossil Reveals Earliest Amniote Breathing System

4/25/2026

Summary

Story summary

Scientists identified protein fragments in a 289-million-year-old Captorhinus fossil, the oldest such molecules reported.
Researchers Ethan Mooney and Robert R. Reisz reported that a Captorhinus specimen from Richards Spur, Oklahoma, shows the earliest rib-based breathing system in amniotes.
Neutron computed tomography in Australia revealed skin, calcified cartilage and a segmented cartilaginous sternum without damaging the specimen.
The researchers said rib-muscle respiration likely enabled early reptiles to adopt more active terrestrial lifestyles.

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Story summary

Scientists identified protein fragments in a 289-million-year-old Captorhinus fossil, the oldest such molecules reported.
Researchers Ethan Mooney and Robert R. Reisz reported that a Captorhinus specimen from Richards Spur, Oklahoma, shows the earliest rib-based breathing system in amniotes.
Neutron computed tomography in Australia revealed skin, calcified cartilage and a segmented cartilaginous sternum without damaging the specimen.
The researchers said rib-muscle respiration likely enabled early reptiles to adopt more active terrestrial lifestyles.