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Fossil poop balls reveal secrets of lost world

July 19, 2009
Courtesy Wiley-Blackwell Journals
and World Science staff

A new study has re­vealed an intricate net­work of long-ago in­ter­ac­tions among bur­row­ing crea­tures in 30-mil­lion-year old fos­sil “mega-dung” from gi­ant mam­mals.

The size­a­ble glob­ules were cre­at­ed by an­cient dung-bee­tles in­tent on stor­ing food for their off­spring.

The South Amer­i­can Scar­ab Dung Bee­tle (Oxys­ter­non con­spicil­la­tum; pho­to cour­te­sy U.S. Nat'l Sci­ence Founda­tion)

The dung-bee­tle has fall­en on hard times. Wor­shipped by the an­cient Egyp­tians, its sta­tus has now slipped to that of un­sung and for­got­ten he­ro, the butt of sca­to­lo­g­i­cal jokes. 

Yet the dung-bee­tle is indeed a he­ro, ac­cord­ing to bi­ol­o­gists. Were it not for the gem-like in­sect, the world would be knee-deep in an­i­mal drop­pings, es­pe­cially those of large plant-eaters like cows, rhi­nos and ele­phants which, be­cause they eat more food, pro­duce more waste. 

By bur­y­ing that waste, dung-bee­tles not only re­move it from the sur­face, they im­prove and fer­ti­lise the soil and re­duce the num­ber of disease-carrying flies that would in­fest the waste.

If the mod­ern dung bee­tle de­serves praise for these glob­al sanita­t­ion ef­forts, then the ex­tinct dung bee­tles of an­cient South Amer­i­ca de­serve a med­al, say Ar­gen­tine re­search­ers stu­dying their fos­sil left­overs.

Thir­ty mil­lion years ago the con­ti­nent was home to what is known as the South Amer­i­ca Mega­fauna, in­clud­ing some truly gi­ant ex­tinct plant-eaters: bone cov­ered ar­madil­los the size of a small car, ground sloths six me­tres (20 feet) tall and elephant-sized hoofed-mam­mals un­like an­y­thing alive to­day. 

Of course, megafauna would have pro­duced mega-dung. The bee­tles had their work cut out for them. The in­sects them­selves didn't fos­silize, but we know they were fully in busi­ness be­cause the re­sults of their ac­ti­vi­ties are pre­served as fos­sil dung balls, some more than 40 mil­lion years old, and some as large as ten­nis balls, the re­search­ers say.

Now the Ar­gen­tine palaeon­tol­o­gists have found that these glob­ules 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, the re­search­ers re­port traces made by oth­er crea­tures with­in fos­sil dung balls.

"Some of these are just the re­sults of chance in­ter­ac­tions" said grad­u­ate stu­dent Vic­to­ria Sánchez of the Ar­gen­tine Mu­se­um of Nat­u­ral Sci­ences in Buenos Aires, one of the in­ves­ti­ga­tors. "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,” she con­tin­ued. “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."

The stu­dy, by Sánchez and Jor­ge Genise of the Egidio Fer­uglio Pa­le­on­to­logical Mu­se­um in Chubut, Ar­gen­ti­na, ap­pears in the July 16 on­line is­sue of the re­search jour­nal Pal­ae­on­tol­ogy.

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A new study has revealed a complex network of interactions among long-ago burrowing creatures in 30-million-year old fossil “mega-dung” from extinct, giant mammals. The sizeable globules were created by ancient dung-beetles intent on storing food for their offspring. The dung-beetle has fallen on hard times. Once worshipped by the Ancient Egyptians, its status has now slipped to that of unsung and forgotten hero, the butt of scatological jokes. Yet the dung-beetle is a hero, according to biologists. Were it not for the gem-like insect, the world would be knee-deep in animal droppings, especially those of large plant-eaters like cows, rhinos and elephants which, because they eat more food, produce more waste. By burying that waste, dung-beetles not only remove it from the surface, they improve and fertilise the soil and reduce the number of disease-carrying flies that would infest the waste. If the modern dung beetle deserves praise for these global sanitation efforts, then the extinct dung beetles of ancient South America deserve a medal, say Argentine researchers studying their fossil leftovers. Thirty 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 six metres (20 feet) tall and elephant-sized hoofed-mammals unlike anything alive today. Of course, megafauna would have produced mega-dung. The beetles certainly had their work cut out for them and although the dung-beetles themselves did not fossilize, we know they were fully in business because the results of their activities are preserved as fossil dung balls, some more than 40 million years old, and some as large as tennis balls, the researchers say. Now the Argentine palaeontologists have found that these globules 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, the researchers report traces made by other creatures within fossil dung balls. "Some of these are just the results of chance interactions" said graduate student Victoria Sánchez of the Argentine Museum of Natural Sciences in Buenos Aires, one of the investigators. "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,” she continued. “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." The study, by Sánchez and Jorge Genise of the Egidio Feruglio Paleontological Museum in Chubut, Argentina, appears in the July 16 online issue of the research journal Palaeontology.