Ancient beetle species discovered in 230-million-year-old reptile dung
There is a new way to learn about ancient insects with the discovery that we can find fossilised beetles inside prehistoric animal droppings.
Martin Qvarnström at Uppsala University in Sweden his colleagues made the discovery by scanning 230-million-year-old fossilised droppings – or coprolites – using a technique called synchrotron microtomography.
“It works a bit like a CT scanner in the hospital, but with a much stronger energy, so we’re able to see small density contrasts within fossils,” says Qvarnström. “It’s like [the coprolites] are doing a part of the fieldwork for us by collecting the insects.”
A large number of beetle fragments along with a few nearly whole beetles were preserved three-dimensionally in the coprolites.
The beetles – the first to be described from ancient dung – belong to a new species, which the researchers have named Triamyxa coprolithica. It was probably semiaquatic had a convex body shape, says Qvarnström. “Boat shaped almost. Very small cute.”
“To get fossilised remains of this quality, researchers have relied in the past on finding them in amber (fossilised tree resin),” says Jesus Lozano-Fernandez at the Institute of Evolutionary Biology in Barcelona, Spain. “The novelty here is the possibility of looking at what is inside of the opaque fossilised poo.”
The earliest amber deposits formed about 140 million years ago early in the Cretaceous period, meaning we can’t rely on amber to learn about beetle evolution before that.
These coprolites allow us to learn about this ecological relationships in an earlier period called the Triassic.
The droppings containing T. coprolithica probably came from Silesaurus opolensis, a reptilian dinosaur relative which ate these beetles in large numbers.
“It gives a unique glimpse into at least a portion of the diet enjoyed by an early reptilian sister to the dinosaurs,” says Michael Engel at the University of Kansas. “Today, some semiaquatic beetles can be found in exceptionally high numbers on algae at seeps other water sources, suggesting that perhaps a similar ecology in these ancient beetles may have afforded a locally abundant source of food.”
Journal reference: Current Biology, DOI: 10.1016/j.cub.2021.05.015
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