Once upon a time, a small reptile was at work when it dropped into the mud before getting up and continuing with its day.

Almost 300 million years later, that brief hiatus has yielded the world’s oldest known fossilized remains of reptile skin, complete with scales and, surprisingly, what scientists interpret as belonging to this creature. cloacaa multipurpose opening used by many animals to poop, pee, copulate, and lay eggs.

“Such soft tissue structures are extremely rare in the fossil record, and the further back in Earth’s history we go, the more exceptional they become.” says paleontologist Lorenzo Marchetti. Collection of the German Natural History Museum in Berlin.

“Signs from the Thuringian Forest provide new perspectives on the early development of reptiles and their skin structure.”

The fossil was excavated from the sedimentary Goldlauter Formation in Germany’s Thuringian Forest Basin, and analysis of the traces left behind revealed it was made by a reptile about 9 centimeters (3.5 inches) long.

Marchetti and his team named this trace a fossil. Cabaljichnus purcululusrepresenting a resting trace of a newly described reptile species.

Its size and nearby footprints suggest that: C.Purculus It was probably a borosaurid, an early branch of the reptilian lineage. They lived during the Epoch Epoch, about 295 million years ago. Athelian period of the Early Permianwhen there were reptiles, starting to diversify rapidly.

The mud left clear traces of what appeared to be abdominal scales, structures made of hard keratin that acted as armor. But the real highlight is at the base of the tail, where modified scales surround a vent-like opening – looking like a cloaca.

Breaking the previous record, be Psittacosaurus butt hole Dating back approximately 120 million years, it is now the “oldest fossil record of a total vent”. amniotes“, The researchers write in their paper: This supports the long-held view that a cloaca was present in early reptiles.

Related: New research suggests your butthole once had a completely different purpose

Interestingly, C.PurculusThe shape and orientation of the cloaca are Psittacosaurusother dinosaurCrocodile. Rather, they resemble the buttholes of turtles, lizards, and snakes.

The fossil also preserves rows of polygonal skin scales spanning the torso, limbs, head, and tail. The researchers discovered that these were epidermal scales, made of keratin like in modern reptiles, rather than the older bony skin armor.

“Trace fossils are much more than just footprints.” marchetti says. “They preserve anatomical details that would otherwise be completely lost and play an important role in improving our understanding of the evolution of early terrestrial vertebrates.”

This study current biology.