Fossil “coprolites” as wide as 40cm and weighing several kilograms were found in seven massive patches across the Chanares Formation in La Rioja province.

Some were sausage-like, others pristine ovals, in colours ranging from whitish grey to dark brown-violet.

“There is no doubt who the culprit was,” said Dr Lucas Fiorelli, of Crilar-Conicet, who discovered the dung heaps.

“Only one species could produce such big lumps – and we found their bones littered everywhere at the site.”