Chinese Fossil Reveals Oldest Preserved Internal Organs of a Marine Reptile

Researchers have analyzed a fossil of the marine reptile Austronaga minuta found in China, which contains the oldest known preserved stomach, liver, and intestinal soft tissue in reptiles. The findings, published in the journal Science Advances, describe a specimen from the Early Triassic period dated between 240 and 245 million years ago. Found in the Yunnan province, the animal measured approximately 60 centimeters in length with a narrow snout and fang like teeth used for capturing fish.

The fossil provides a rare look at the internal anatomy of early reptiles before the Era of Dinosaurs. The specimen featured a single chambered stomach and a simple, straight intestinal tract containing identifiable fish scales. Researchers also noted that the liver maintained a red color due to preserved hemoglobin residues with high iron content. Anatomically, the creature was an agile swimmer that used its tail for propulsion and large front flippers for steering.

The discovery offers insight into how early stem archosaurs evolved aquatic specializations during the transition from land to sea. While researchers are uncertain if the specimen was a fully grown adult, it represents one of the earliest known examples of a reptile with unequivocal aquatic adaptations.