Scientists have discovered a 245-million-year-old fossil of a tiny marine predator with its soft internal organs intact, making it the oldest reptile ever found with a preserved digestive system. Found in China's Yunnan province in 2023, the specimen—named Austronaga minuta—offers researchers a rare window into the internal biology of ancient sea creatures from the Triassic Period.
Remarkably, the fossil preserves nearly the entire skeleton alongside clear outlines of the stomach, liver, and intestines. Under close examination, researchers could even identify ancient blood vessels and the delicate scales of the animal's last meal—a partially digested fish. Experts outside the study have hailed the specimen as a global treasure due to its extraordinary state of preservation.
Austronaga minuta grew to about 60 centimeters in length and belonged to the archosaurs, a diverse group of reptiles that includes modern crocodiles and birds, as well as extinct dinosaurs. Unlike larger relatives such as the four-meter-long Dinocephalosaurus, Austronaga was likely a small, agile swimmer that used its long tail for propulsion, flippers for steering, and long neck to catch fish.
The discovery also highlights how little reptilian digestion has changed over hundreds of millions of years. The fossil's straight and simple digestive tract closely resembles the intestines of modern fish-eating predatory reptiles. Although the soft organs were compressed into two dimensions over time, the level of detail provides invaluable insights into early reptile evolution.