Chinese fossil shows internal organs of prehistoric marine reptile

Key Points:

• Scientists discovered a 245-million-year-old fossil of Austronaga minuta, a long-necked marine reptile from the Triassic Period, in Yunnan Province, China, revealing exceptionally preserved internal organs including stomach, liver, and intestines.
• Austronaga was about 2 feet long, with a small head, fang-like teeth for catching fish, a long neck and tail, and used its tail for propulsion and front flippers for steering, indicating high aquatic adaptation among archosaur relatives.
• The fossil shows Austronaga had a simple, single-chambered stomach, suggesting the evolution of the double-chambered stomach in archosaurs occurred later, closer to the origin of birds and crocodiles.
• Remarkably, the liver retained red coloration due to preserved hemoglobin residues, and the digestive tract contained fish scales, confirming its predatory diet and providing rare insight into early reptilian anatomy.
• Austronaga lived in a warm, shallow equatorial sea alongside larger marine predators like nothosaurs, and while the specimen’s maturity is uncertain, it was likely a small marine reptile that did not grow to large sizes.