A fossilized grasshopper nest discovered in Oregon may be one of a kind

(CNN) — In an ancient temperate forest in what is now Oregon, an insect burrowed deep into a sandbar near a stream. There, in a damp pit, she laid dozens of elongated eggs, about 50 in all. Despite their careful work to build this underground shelter, not one of the eggs ever hatched. Instead, the egg, encapsulated like a pod, becomes fossilized in a mineralized, stony mass.

And now, 29 million years later, they stand as a record of insect reproduction that may be unlike anything paleontologists have ever seen.

A recent micro-CT scan of the eggshell revealed that not only is it millions of years old, but it was most likely the work of a grasshopper. The egg and general nest construction closely resemble the eggs and capsules of modern grasshopper species. This new documentation provides a clearer picture of that ancient ecosystem, confirming that grasshoppers were present and thrived there, and that some types of grasshoppers buried their eggs underground.

Insect eggs are extremely rare in the fossil record, and intact egg pods are even rarer. This is perhaps the only known fossil grasshopper egg capsule, and provides insight into their reproduction during the Oligocene epoch (between 33.9 and 23 million years ago).

“This work is exciting because such extraordinary preservation provides unique insight into one of the least understood phases of insect life, particularly in the geological past,” Jaemin Lee, lead author of the study, told CNN in an email. , evolutionary ecologist and doctoral. student at the University of California at Berkeley.

Intact fossilization

What makes this fossil even more remarkable is that it was found in a habitat that is not normally conducive to fossilization, study co-author Dr. Nick Famoso, paleontology program manager and museum curator of the monument. National John Day Fossil Bed. Located in Mitchell, Oregon, this site is managed by the National Park Service.

Fragile fossils like this specimen are usually preserved in lake deposits along with plant matter. Famoso explains that these places are generally anoxic, or low in oxygen, and relatively stagnant. There, the remains can move quietly, untouched by currents or bacteria. But millions of years ago no river or canal passed through this place. However, despite the dynamic environment of flowing water nearby, the conditions surrounding this egg capsule were perfect for it to be buried and remain intact, Famoso explained.

These fossil eggs differ in their preservation, “individually and collectively,” paleobiologist Dr. said Ricardo Pérez-de la Fuente, deputy head of research at the Museum of Natural History at the University of Oxford in the United Kingdom. Email. United.

“They are the first Orthoptera (grasshoppers and the like) identified in the fossil record, which is noteworthy,” says Pérez-de la Fuente, who was not involved in the research.

“It also represents an important step towards formalizing the description of the immature stages of insects, especially the eggs,” Pérez-de la Fuente said. This branch of science, known as autaxonomy, “can provide essential data on the evolution, behavior and ecology of insects in deep time, but which are neglected in paleontological studies.” Additionally, he added, capsules and eggs can provide clues about the environment in which they fossilized.

unusual curve

National Park Service collections manager Christopher Schirp discovered the egg case at the fossil site in July 2012. Schierp was conducting a routine visual inspection of the site when he spotted the object, which was embedded in a piece of rock. Rolling down the hill, Famoso remembered.

“No tools need to be used to pull it out of the ground,” he said. Schirp wrapped the object in toilet paper “and carefully returned it to the visitor center where our laboratory is located,” Famoso added.

National Park Service collections manager Christopher Schirpp first saw the fossil in 2012 at the John Day Fossil Beds National Monument in Mitchell, Oregon. Credit: N. Famoso/National Park Service

Based on analysis of the fossil’s surface, the researchers initially thought they had found a mass of ant eggs. But Famoso was skeptical, as its curvature differed from the curvature of ant eggs and pupae. His suspicions were confirmed by Lee, who saw the object for the first time in 2022 during a visit to the John Day Fossil Beds. They took the sample to the University of Oregon’s Knight Campus in Eugene, where study co-author Angela Lin, director of the X-ray Imaging Research Core Facility, performed micro-CT scans.

“That’s when we discovered that there was a layer of protein that held everything together,” Famoso explains.

This was not just a mass of eggs, but a kind of underground egg capsule called an otheca, in which the eggs were covered with a protective layer that had mineralized in the crust of the rock.

“Currently, only two groups of insects produce underground oothecae,” Lee explains. These are grasshoppers (order Orthopterasuborder Calyfera) and studs (order Mantophasmatodia).

Radial arrangement

On the surface were 28 oval eggs, each no more than 4.65 millimeters long and 1.84 millimeters wide (these are comparable to modern grasshopper eggs, although egg size can vary by species). Scans revealed more than two dozen eggs buried in the matrix in four or five layers arranged in a radial pattern. Some eggs were hollow, while others were filled with sediment, the study authors reported.

“The mineralization that we could see in each egg made it very clear that it was a fossilized structure,” Famoso said.

Because fossil insect eggs are so rare, there were not many specimens available for comparison. So Lee consulted a global database of insect eggs, which contains more than 6,700 living species, to identify eggs from fossil capsules.

“I compared the egg’s defining characteristics, such as size, length-width ratio, and curvature of each egg, with those of live eggs,” he explained. “Such large, elliptically curved eggs and large clutch sizes (50 eggs in total) are unknown in any other group of living insects except grasshoppers and locusts.”

The unusual discovery provides a never-before-seen view of reproduction in ancient relatives of modern grasshoppers. The practically pristine specimen also shows the level of preservation of the national park’s fossil beds, Famoso added.

“Just being able to see the interior structure and properly describe what it looked like was really exciting for us,” Famoso said. “There is nothing in the fossil record that we know of.”

— Mindy Weisberger is a science writer and media producer whose work has appeared in Live Science, Scientific American, and How It Works magazine.