Beetles are everywhere—and new members of Earth’s most diverse group of organisms are being discovered nearly every day. Now, for the first time, scientists have found a new species in an unusual place: the fossilized poop of a dinosaur ancestor. Found whole and remarkably intact, the 230-million-year-old beetle, named Triamyxa coprolithica, is the first insect to be scientifically described from fossilized feces, also known as coprolites.
“This is very exciting research,” says Spencer Lucas, a paleontologist at the New Mexico Museum of Natural History and Science, who was not involved in the work. “This study is cutting edge and explores a whole new area of paleontology that has only been understood in the last decade.”
Coprolites are abundant in museum and research collections around the world. But until recently, Lucas says, few scientists examined these “little capsules of incredible fossil record” for their content, largely because researchers did not think small insects could successfully pass through a digestive system and end up in a recognizable form. Instead, paleontologists got most of their information about insect evolution from unlucky ones trapped in amber, or fossilized tree resin. But these fossils aren’t very old, geologically speaking: The most ancient ones date back to about 140 million years ago.
To discover whether coprolites could indeed preserve insect remains, Uppsala University paleontologist Martin Qvarnström and colleagues examined fossilized droppings from Poland that has previously been associated with the Triassic period, some 230 million years ago. They selected a coprolite fragment nearly 2 centimeters long that, based on its broken ends, suggested it was part of a much larger piece that might be more likely to contain things inside it. Then, they subjected the whole specimen to an intense x-ray beam at a synchrotron. By rotating the coprolite in the beam, they created 3D reconstructions of the coprolite’s contents. What they saw astounded them: incredibly preserved, nearly complete insects just 1.4 millimeters long, as well as fragments like heads, antennae, and legs, they report today in Current Biology.
The new species came from dung presumed to have been excreted by Silesaurus opolensis, a beaked dinosaur ancestor about 2.3 meters in length. The beetles were well preserved because coprolites act as microenvironments that can preserve organic material, including soft tissues, without any of the flattening that comes with other fossil types.
This extinct beetle likely belonged to a group known as Myxophaga, small beetles that thrive on algae in wet habitats, says study co-author Martin Fikáček, an entomologist at National Sun Yat-sen University. The team categorized it taxonomically by noting shared characteristics, like the number of abdomen segments or the position of the antennae, to modern Myxophaga, of which four lineages still survive today. The find is remarkable, Qvarnström says. “We have found bits and pieces [of insects in fossilized feces] before, but not enough to describe a new species, genus, and family,” like this.
These reconstructed images and models (see video above) not only reveal the new beetle species, but also offer information about the diets and environments of the animals that ate them, Qvarnström says. Such analyses can help scientists understand ancient food webs and how the dinosaur ancestors lived and interacted in this ancient ecosystem. By scanning coprolites from earlier and later in the Triassic period, the team also hopes to learn about insect evolution.
As for T. coprolithica, researchers say there is no way of knowing why it went extinct while its cousins survived into the modern era. Fikáček says it is likely to have been a combination of random events and sheer bad luck. “Extinction is always the trickiest part out of all these things to understand,” he says.