Fossil grasshopper nest discovered in Oregon may be one-of-a-kind

(CNN) — Now in an ancient temperate forest in Oregon, an insect was hiding deep in a pile of sand near a stream. There, in a moist burrow, she lays dozens of elongated eggs, about 50 in total. Despite their careful work in building this underground shelter, none of the eggs ever hatched. Instead, the eggs, encased like a pod, became fossilized in a mass of mineralized, stone.

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

Recent micro-CT scans of the eggshell revealed not only that it was millions of years old, but also that it was likely the work of a grasshopper. The eggs and general nest structure closely resemble the eggs and capsules of modern grasshopper species. This new document paints a clearer picture of that ancient ecosystem, confirming that locusts were present and thriving there, and that some types of locusts buried their eggs underground.

Insect eggs are extremely rare in the fossil record, and intact egg pods are even rarer. It is possibly the only known fossil locust egg capsule, and provides information about their reproduction dating back to the Oligocene epoch (33.9 and 23 million years ago), researchers reported Monday in the journal Parks Stewardship Forum.

“This work is exciting because such extraordinary preservation provides unique insight into one of the least understood stages of insect life, especially in the geological past,” Jaemin Lee, lead author of the study, told CNN in an email. ” 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 typically conducive to fossilization, said study co-author Dr. Nick Famoso, paleontology program manager and museum curator of the monument. , said the National John Day Fossil Beds. Located in Mitchell, Oregon, the site is managed by the National Park Service.

Fragile fossils such as this specimen are usually preserved in lake deposits along with plant matter. Famoso explains that these places are usually anoxic, or low in oxygen, and relatively stable. There, fossils can form quietly, untouched by currents or bacteria. But millions of years ago a river or drain used to pass through this place. However, despite the dynamic environment of nearby flowing water, the conditions around this egg capsule were just right for it to remain buried and intact in almost perfect conditions, Famoso reported.

The fossil eggs are important for their preservation “both individually and together,” said paleontologist Dr. Ricardo Pérez-de la Fuente, deputy head of research at the Museum of Natural History at the University of Oxford, United Kingdom. E-mail. United.

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

“This work represents an important step toward formalizing the description of the immature stages of insects, particularly eggs,” said Pérez-de la Fuente. This branch of science, known as ootaxonomy, “can provide essential data on the evolution, behavior, and ecology of insects in deep time, but is ignored in the study of paleontology.” Additionally, he said, capsules and eggs may provide clues about the environment in which they were fossilized.

abnormal curvature

Christopher Schierup, collections manager for the National Park Service, discovered the egg cases at the fossil sites in July 2012. Schierup was making a routine visual inspection of the site when he noticed the object, which was embedded in a piece of rock. Rolled down the hill, Famoso recalled.

“There was no need to use any equipment to get it out of the ground,” he said. Schierup wrapped the object in toilet paper and carefully returned it to the visitor center, where our laboratory is located, Famoso said.

Christopher Schierup, collections manager for the National Park Service, 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, researchers initially thought they had found a clutch of ant eggs. But Famoso was skeptical, because its curvature was different from the curvature of an ant’s egg and pupa. His suspicions were confirmed by Lee, who first saw the object during a trip to the John Day Fossil Beds in 2022. They took the samples to the University of Oregon’s Knight Campus in Eugene, where Angela Lynn, co-author of the study and director of the X-ray Imaging Research Core Facility, conducted a micro-CT scan.

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

It was not simply a cluster of eggs, but a type of underground egg capsule called an ootheca, in which the eggs were covered with a protective layer that had mineralized into the layer of stone.

“Currently, only two groups of insects produce underground oothecae,” explains Lee. These are locusts (order Orthopterasub-order caelifera) and std ( order Mantophasmatodea,

radial arrangement

There were 28 ellipsoidal eggs on the surface, each no more than 4.65 millimeters in length and 1.84 millimeters in width (this is comparable to modern locust eggs, although the size of the eggs can vary depending on the species). Scans revealed more than two dozen eggs buried in the matrix in four or five layers, arranged in a radial pattern. The study authors reported that some of the eggs were hollow, while others were filled with sediment.

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

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

“I compared the defining characteristics of the eggs, such as size, length-width ratio and curvature of each egg, to living eggs,” he explained. “Such large, elliptically curved eggs and large clutch size eggs (about 50 eggs in total) are unknown in any other group of living insects apart from grasshoppers and locusts.”

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

“It was really exciting for us to be able to see the internal structure and accurately describe what it looks like,” Famoso said. “There’s nothing in the fossil record that we know of.”

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