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Ancient cockroaches dined on dino dung

Cleaning up During the reign of the dinosaurs, more than 65 million years ago, the humble cockroach ensured the ground wasn't always covered in a layer of dung, according to a new study.

Like cattle, camels and other herbivores of our time, sauropods (large plant-eating dinosaurs) ate a lot of plant material, and as a result left a lot of dung in their wake.

Today the job of breaking down dung is mostly performed by flies and dung beetles. Without them, the ground becomes 'suffocated' and grasses are unable to grow.

During the 1960s, the absence of dung beetles capable of breaking down dung from sheep and cattle, resulted in soil degradation across many parts of Australia -- along with a huge increase in flies. This led to the introduction of dung beetles from South Africa to help control the problem.

But dung beetles and flies were rare during the Mesozoic. So who was responsible for breaking down dino dung?

The answer has been found by a team of scientists, led by Peter Vršanský of the Slovak Academy of Sciences, looking at an ancient family of cockroaches known as Blattulidae.

The team examined a cockroach, along with coprolites (or fossilised faeces) it had "extruded", which were trapped in an amber deposit found in Lebanon. They used synchrotron x-ray microtomography, which allowed the researchers to build a 3D image of the roach and its droppings, without breaking it from its amber encasing.

Like other cockroaches from that time, the contents of the gut and the coprolites showed the insect had a varied diet. But there was something else that caught their eye.

"The occurrence of any wood … was entirely unexpected," they write in their report which appears in the journal PLOS ONE .

The coprolites contained particles of wood with smooth edges, suggesting they were digested before the cockroach ate them.

"The wood was apparently processed before it entered the cockroach digestive tract," they write. "The only possible explanation is that these were caused by herbivorous vertebrates."

"Due to the dominance of these cockroaches for the same 200 million years as dinosaurs, no other vertebrate group is as promising for this candidature."

The Blattulidae family of cockroaches are no more, but thankfully flies and dung beetles have stepped up to the task.

However, the researchers note that there are some cockroaches that continue to feast on the dropping of other animals, such as bats, geckos, cattle and birds - the later thought to have evolved from the dinosaurs.