This 245 Million-Year-Old Marine Reptile Still Has Most of Its Digestive Tract — One of the Oldest Ever Found

A 245-million-year-old marine reptile, Austronaga minuta, has provided scientists with one of the most complete digestive tracts ever discovered, according to a study published in Science Advances. The fossil, found in China, reveals a nearly intact digestive system, shedding light on the evolutionary development of reptilian stomachs.

Unlike modern birds and crocodiles, which possess a two-part stomach, Austronaga possessed a single stomach chamber. The research team, comprised of international experts, utilized advanced technologies such as UV light photography and mass spectrometry to analyze the fossilized remains, leading to a detailed examination of the reptile's skeleton and digestive tract.

Austronaga, a 2-foot-long marine reptile, had a long neck and tail that propelled it through water, along with front fins for steering and smaller back fins that likely did not aid in swimming. Its unique body structure places Austronaga more closely related to archosaurs, a land-dwelling group that includes dinosaurs and crocodiles, rather than other marine reptiles like ichthyosaurs.

The study's lead author, Wei Wang, describes the preserved organs, including a large, sac-like stomach and a long, simple tube forming the small and large intestines, as indicative of a relatively simple digestive system structure in Austronaga.