We can learn a lot about extinct giant South American mammals from 30-40 million years ago thanks the random process of fossilization.    Even their ancient 'mega-dung' has a tale to tell scientists and we can thank the unheralded dung beetle.

The dung beetle has fallen on hard times. Though once worshipped by the Ancient Egyptians its status has now slipped to being the butt of scatological jokes.

Yet a wise few still consider the dung beetle heroic.  Example: if not for the dung-beetle the world would be knee-deep in animal droppings, especially the big herbivores like cows, rhinos and elephants who eat a lot of food and produce almost as much waste.  Dung beetles bury that waste and not only remove it from the surface, they improve and fertilize the soil and reduce the number of disease-carrying flies that would otherwise infest the dung.

If you like modern dung beetles, you'd really love the extinct dung beetles of ancient South America.  30 million years ago the continent was home to what is known to palaeontologists as the South America Megafauna, including some truly giant extinct herbivores: bone covered armadillos the size of a small car, ground sloths 6 metres tall and elephant-sized hoofed-mammals unlike anything alive today.  Those megafauna produced mega-dung.

No dung beetle fossils have been found but we know they were taking care of business because, amazingly, some of their work is preserved as fossil dung 'balls', some more than 40 million years old, and some as large as tennis balls.

Palaeontologists in Argentina studying these dung balls have discovered that they have even more to tell us about the ecology of this lost world of giant mammals, but at a rather different scale. In a study published in the latest issue of the journal Palaeontology, Graduate Student Victoria Sánchez and Dr Jorge Genise report traces made by other creatures within fossil dung balls.

"Some of these are just the results of chance interactions" explains Dr Sánchez. "Burrowing bees, for example, dug cells in the ground where the dung balls were buried, and some of these happen to have been dug into the balls. But other traces record the behaviour of animals actively stealing the food resources set aside by the dung beetles. The shapes and sizes of these fossilized burrows and borings in the dung balls indicate that other beetles, flies and earthworms were the culprits. Although none of these animals is preserved in these rocks, the fossil dung balls preserve in amazing detail a whole dung-based ecosystem going on right under the noses of the giant herbivores of 30 million years ago."