Named Triamyxa coprolithica, the tiny beetles are also the first insects to be described from fossilized feces – or coprolites – and were visible by a scanning method using powerful x-ray beams, according to a study published Wednesday in the journal Current Biology. . Besides the discovery of beetles in a coprolite, the scientific name also refers to the Triassic Period, which lasted from around 252 million to 201 million years, and the insect suborder called Myxophaga – small aquatic beetles or semi-aquatic that eat algae.
“Insect fossils of this type, preserved in three dimensions like this one, are virtually unknown to the Triassic, so this find is very important,” said Sam Heads, director and chief curator of the PRI Center for Paleontology at the ‘University of Illinois at Urbana-Champaign, by e-mail. Heads was not involved in the study.
“I was really amazed at how well preserved the beetles were, when you modeled them on screen it was like they were looking you straight in the eye,” the lead author said. study, Martin Qvarnström, paleontologist and postdoctoral fellow at Uppsala University. , Sweden, in a press release. “This is facilitated by the calcium phosphate composition of the coprolites. This, combined with early mineralization by bacteria, likely helped preserve these delicate fossils. “
Calcium phosphate is essential for building and maintaining bones, and mineralization occurs when organic compounds are converted to inorganic compounds during decomposition processes.
“Silesaurus had a beak at the end of its jaws that could have been used to root in litter and possibly peck insects on the ground, much like modern birds,” according to a press release.
“Although Silesaurus appears to have ingested many individuals of Triamyxa coprolithica, the beetle was probably too small to have been the only prey targeted,” Qvarnström said. “Instead, Triamyxa likely shared its habitat with larger beetles, which are represented by disarticulated remains in coprolites, and other prey, which never found themselves in coprolites in any recognizable form. It therefore seems likely that Silesaurus was omnivorous, and that part of his diet was made up of insects. “
There is not “enough evidence at this point to say for sure whether Silesaurus specifically selected these beetles,” Heads said.
“It is possible that it was a generalist insectivore catching all the insects it could catch and that the beetles were the only ones to survive digestion thanks to their (very hard and) robust exoskeletons.” added Heads. “Their small size would certainly have helped some of them stay intact because they were more likely to be swallowed whole and not chewed.” »
Another suggestion made by the researchers, based on their findings, is that coprolites could be an alternative to another material known to produce the best-preserved insect fossils: amber, the hard fossilized resin, yellowish but translucent produced by extinct Tertiary trees. period, which lasted from about 66 million to 2.6 million years ago.
“I have worked with fossil insects preserved in amber for many years and agree with the authors that the level of preservation observed in coprolite specimens is very similar in terms of completeness and retention level, ”Heads said. “It’s really quite remarkable. “
Since the oldest amber fossils are around 140 million years old, the much older coprolites could help researchers venture further into the unexplored past, according to a press release.
“We didn’t know what the insects looked like in the Triassic and now we have the chance,” study co-author Martin Fikáček, entomologist at National Sun Yat-sen University in Taiwan, said in a statement. “Maybe when many more coprolites are analyzed, we will find that some groups of reptiles have produced coprolites that are not really useful, while others have coprolites full of well-preserved insects that we can study. We just have to start looking inside the coprolites to get at least some idea. “
Researchers who find coprolite insects can scan them in the same way scientists scan amber insects, Fikáček added, which would reveal minute details. “In this aspect our find is very promising, it basically tells people, ‘Hey, check for more coprolites using the microCT, there’s a good chance you’ll find insects there, and if you find it, it can. to be really well preserved. “”
The study team’s ultimate research goal, said Qvarnström, is “to use data from coprolites to reconstruct old food webs and see how they have changed over time.”