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In an ancient temperate forest in what is now Oregon, a beetle burrowed deep into the sandy bank near a stream. There, in a moist nest, she laid dozens of oblong eggs, about 50 in total. Despite the careful work he did in building this underground nursery, none of the eggs hatched. Instead, the eggs, encased in a shell, fossilized into a stony, mineralized mass. And now, 29 million years later, they stand as a record of insect reproduction unlike anything paleontologists have ever seen before.
Recently, micro-CT scans of the egg box revealed that not only was it millions of years old, but it was also likely made by a grasshopper. The eggs and overall nest structure are very similar to the eggs and shells of modern grasshopper species. This newly documented information paints a clearer picture of this ancient ecosystem; It confirms that grasshoppers are present and thriving there, and that some species of grasshoppers bury their eggs underground.
Insect eggs are extremely rare in the fossil record; Cases of intact eggs are even rarer. This is likely the only fossilized grasshopper eggshell on record, offering a view of their reproduction dating back to the Oligocene Epoch (33.9 million to 23 million years ago), researchers reported Monday in the journal Parks Stewardship Forum.
“This study is exciting because such extraordinary preservation provides unique insights into one of the least understood life stages of insects, particularly the geological past,” said lead study author Jaemin Lee, an evolutionary ecologist and doctoral student at the University of California, Berkeley. he told CNN in an email.
Pristine fossilization
co-author of the study, paleontology program manager and museum curator at the John Day Fossil Beds National Monument. Nick Famoso said that what makes this fossil even more remarkable is that it was found in a habitat that is generally not suitable for fossilization. Located in Mitchell, Oregon, the site is under the management of the National Parks Service.
Delicate fossils like this specimen are often preserved in lake beds alongside plant remains. Famoso explained that such places tend to be anoxic, or oxygen-poor, and relatively static. There fossils can form in peace, untouched by currents or bacteria. However, millions of years ago, a river or stream passed through this region. Still, the conditions surrounding this eggshell were just right for it to remain buried and fossilize intact in nearly perfect condition, despite the dynamic environment of nearby flowing water, Famoso said.
paleobiologist Dr. Ricardo Pérez-de la Fuente said that the eggs in this fossil stand out because they were preserved “both individually and in clusters.” email.
“These are the first creatures identified in the fossil record as belonging to orthopterans (locusts and their relatives),” said Pérez-de la Fuente, who was not involved in the research.
“This study also represents an important step towards formalizing the definition of immature stages of insects, especially eggs,” said Pérez-de la Fuente. This branch of science, known as ootaxonomy, “can provide extraordinary data on the deep-time evolution, behavior, and ecology of insects, but they tend to be neglected in paleontological studies.” What’s more, he added, the shells and eggs may offer clues about the environment in which they fossilized.
Eggs had an unusual curvature
National Parks Service collections manager Christopher Schierup discovered the egg box in the fossil beds in July 2012. While doing a routine visual survey of the area, Schierup noticed the object embedded in a boulder. Famoso recalled rolling down a hill.
“There was no need for any tool work to get it out of the ground,” he said. Famoso added that Schierup wrapped the object in toilet paper and “carefully returned to the visitor center where our laboratory is located.”
Based on surface analysis of the fossil, researchers initially thought they had found a cluster of ant eggs. However, Famoso was skeptical because their curvatures differed from the curvatures of ant eggs and pupae. His suspicions were confirmed by Lee, who first saw the object during a visit to the John Day Fossil Beds in 2022. They brought the sample to the University of Oregon’s Knight Campus in Eugene; where micro-CT scans were conducted by study co-author Angela Lin, director of the X-ray Imaging Research Core Facility.
“That’s when we discovered that there was a protein layer that held everything together,” Famoso said. This wasn’t just a clutch of eggs; It was a type of underground egg capsule called an ootheca; The eggs were surrounded by a protective layer that mineralized into a stony shell.
“Underground eggshells are currently produced by only two groups of insects,” Lee said. These are grasshoppers (order Orthoptera, suborder Caelifera) and heel walkers (order Mantophasmatodea).
radial arrangement
28 ellipsoid eggs were visible on the surface, each no more than 0.18 inches (4.65 millimeters) long and 0.07 inches (1.84 millimeters) wide (this is comparable to modern grasshopper eggs, although egg size may vary depending on the species). ). Scans revealed more than two dozen eggs embedded in four to five layers arranged in a radial pattern in the matrix. The authors of the study reported that some of the eggs were empty, while others were filled with sediment.
“The mineralization we could see in each of the eggs made it clear that this was a fossilized structure,” Famoso said.
Because fossil insect eggs are so rare, there weren’t many examples to compare with. To identify the eggs in the fossil shell, Lee consulted a global database of insect eggs containing more than 6,700 living species.
“I compared descriptive egg characteristics with those of living things, including size, length/width ratio, and curvature of individual eggs,” he said. “Such large, elliptically curved eggs in a large brood size (~50 eggs in total) are not known in other living insect groups other than grasshoppers and locusts.”
This extraordinary find offers a never-before-seen insight into the breeding of ancient relatives of modern grasshoppers. Famoso added that the nearly intact specimen also points to the level of preservation of fossil beds in the national park area.
“Just being able to see this internal structure and really accurately describe what these things look like was a really exciting thing for us,” Famoso said. “There is nothing like it in the fossil record anywhere 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 magazines.
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