The world's oldest communal toilet is littered with thousands of ancient droppings, each a window millions of years into the past.
Sometimes packed as tightly as 94 fossils per square meter, the feces belong to the Dinodontosaurus, an herbivore that weighed several hundred pounds and reached about 8 feet long.
"There is no doubt who the culprit was," Lucas Fiorelli, of Crilar-Conicet, who discovered the dung heaps, told the BBC. "Only one species could produce such big lumps - and we found their bones littered everywhere at the site."
The fossils, called coprolites, were uncovered in Argentina and date back to the Triassic period, making the site 220 million years older than the previously oldest known common latrine. They vary from dark brown-violet to whitish grey. Some are "sausage-like with segmented surfaces" while others are smooth, and oval-shaped, according to the study published in the journal Scientific Reports.
Regardless of the size, shape or color, however, each carries a story inside.
"When cracked open they reveal fragments of extinct plants, fungi, and gut parasites," said Martin Hechenleitner, a study co-author. "Each poo is a snapshot of an ancient ecosystem -- the vegetation and the food chain."
Communal toilets are common among today's mammals, the researchers explain, noting the wide range of biological and ecological functions they serve, including intra- and inter-specific communication, reproduction, defense against predators and the warding off of parasites.
"Firstly, it was important to avoid parasites - 'you don't poo where you eat', as the saying goes," Fiorelli said.
However, because fecal matter is so quick to degrade, fossil records like the one found in Argentina are rare. In all, the site contained eight separate separate coprolite groupings.
According to LiveScience, the researchers plan to excavate the area as well as the fossils further in order to reconstruct what the area would have looked like in terms of vegetation back when the feces were first left.