Scientists have discovered a 230-million-year-old beetle species pristinely preserved in fossilized dung. The species represents a new family of beetles, and likely served as a snack for a dinosaur ancestor in the Triassic period.
The discovery highlights how fossilized dung, called coprolites, can open a window into the past. From offering scientists a look at ancient gut bacterial communities, to sharing secrets about parasites in animals, petrified poop has already proven an important research tool.
"We didn't know how insects looked in the Triassic period and now we have the chance," said Martin Fikáček, an entomologist at National Sun Yat-sen University in Taiwan and co-author of the paper published Wednesday in the journal Current Biology.
As more coprolites are analyzed, scientists may find some harbor nicely preserved insects, Fikáček added.
Fikáček and the research team glimpsed inside the fossil poop using a method called synchrotron microtomography, which works like a hospital CT scanner but with strong X-ray beams. The technique makes it possible to visualize 3D internal structures in fossils with great resolution and contrast.
The researchers found the beetles with their legs and antenna intact. The scientists say the coprolites' chemical composition, along with the early mineralization by bacteria, likely helped preserve the creatures.
"I was really amazed to see how well preserved the beetles were," said paper co-author Martin Qvarnström, a paleontologist at Uppsala University in Sweden. "When you modeled them up on the screen, it was like they were looking right at you."
The scientists named the species Triamyxa coprolithica, referring to its Triassic age, beetle suborder and its discovery in coprolite. Modern representatives of Triamyxa's beetle suborder, Myxophaga, are small and live on algae in wet environments.
In its day, Triamyxa likely lived in semiaquatic or humid environments. The beetles were likely ingested and expelled by Silesaurus opolensis, a beaked dinosaur ancestor that measured roughly 6.5 feet (2 meters) long and lived at the same time as the beetle in what is now Poland.
Silesaurids, which includes Silesaurus opolensis, are one of the closest relatives to Dinosauria. As they lack shared derived features expected in the most recent common ancestor of Iguanodon, Diplodocus, and Megalosaurus and its descendants, Silesaurids do not seem to be true dinosaurs, according to the University of Maryland. The Silesaurus in question appears to have munched on multiple Triamyxa individuals, but scientists say the beetle was probably too small to be the dinosaur ancestor's only target.
"Triamyxa likely shared its habitat with larger beetles, which are represented by disarticulated remains in the coprolites, and other prey, which never ended up in the coprolites in a recognizable shape," Qvarnström said. "So it seems likely that Silesaurus was omnivorous, and that a part of its diet was comprised of insects."
Whether it was the small beetle that Silesaurus found particularly delectable, or something else, it's a good thing it left us with a remnant of its lunch, a rare portal into insect fauna millions of years ago.