(CNN) — In an ancient temperate forest in what is now Oregon, an insect burrows deep in a sandbar near a stream. There, in a damp cave, she laid dozens of elongated eggs, about 50 in total. Despite their careful construction of this underground shelter, not a single egg hatched. Instead, the eggs are encased like pods and fossilized into mineralized rocks.
Now, 29 million years later, they serve as a record of insect reproduction that may be unlike anything paleontologists have seen to date.
Recent micro-CT scans of the eggshell revealed that not only is it millions of years old, but it was likely the work of a grasshopper. The eggs and general nest structure are very similar to those of modern grasshopper species. The new document provides a clearer picture of this ancient ecosystem, confirming that grasshoppers existed and thrived there, and that some types buried their eggs underground.
Insect eggs are extremely rare in the fossil record, and intact egg pods are even rarer. It may be the only known fossilized grasshopper egg capsule and provides insight into reproduction during the Oligocene epoch (33.9 to 23 million years ago), researchers reported Monday in the journal Park Management Forum.
Jaemin Lee, the study’s lead author, told CNN in an email: “This work is exciting because this exceptional preservation provides unique insights into one of the least understood life stages of insects, especially when in Geological History.” student at the University of California, Berkeley.
What’s even more remarkable about this fossil is that it was found in a habitat not typically conducive to fossilization, said study co-author Dr. Nick Famoso, paleontology program manager and museum curator at the National John Dee Fossil Beds Monument. of. The site is located in Mitchell, Oregon, and is managed by the National Park Service.
Delicate fossils like this specimen are often preserved in lake sediments along with plants. Famoso explained that these places are often anoxic, or have low oxygen levels, and are relatively still. There, fossils can form quietly, unaffected by water flow or bacteria. But millions of years ago, a river or stream flowed through this place. However, Famoso explained that the conditions surrounding this egg sac were suitable for it to remain buried and fossilize intact in near-perfect conditions, despite the dynamics of the nearby water flow environment.
Dr. Ricardo Pérez-de la Fuente, a paleontologist and deputy director of research at the University of Oxford’s Museum of Natural History, said in a report that the fossil’s eggs stood out for their “preservation both individually and as a whole.” Email.Union.
“It’s remarkable that they are the earliest orthopterans (grasshoppers, etc.) found in the fossil record,” said Pérez-de la Fuente, who was not involved in the study.
“This work also represents an important step in the description of immature stages of insects, more specifically insect eggs,” said Pérez-de la Fuente. This branch of science, known as otic taxonomy, “can provide “Important data on the evolution, behavior and ecology of insects in ancient times, but which are often overlooked in paleontological studies.” Additionally, he added, the capsules and eggs may provide clues about the environment in which they fossilized.
Christopher Schierup, collections manager for the National Park Service, discovered the egg carton at the fossil site in July 2012. When Schirup was conducting a routine visual inspection of the site, he discovered the object, embedded in a rock that sent him rolling down the hill, Famoso recalled.
“You don’t have to use any tools to get it out of the ground,” he said. Schirup wrapped the object in toilet paper “and then carefully returned to the visitor center where our laboratory is located,” Famoso added.
Based on analysis of the fossil’s surface, researchers initially thought they had discovered a cluster of ant eggs. But Famoso was skeptical because its curvature was different from that of ant eggs and pupae. His suspicions were confirmed by Lee, who first saw the object while visiting the John Day Fossil Beds in 2022. They took the samples 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 there’s a layer of protein that holds everything together,” Famoso explained.
This is not just a cluster of eggs, but an underground egg sac called an ootheca, in which the eggs are surrounded by a protective layer mineralized into a stone shell.
“Currently, only two types of insects produce underground egg sheaths,” Li explained.These are grasshoppers (order OrthopteraSuborder Kelly Ferra) and studs (order Manterozoology).
There are 28 oval-shaped eggs on the surface, each of which is no more than 4.65 mm in length and 1.84 mm in width (this is comparable to the eggs of modern grasshoppers, although the size of the eggs may vary depending on the species). Scans showed more than two dozen eggs buried in the matrix, divided into four or five layers and arranged in a radial pattern. Some eggs were hollow, while others were filled with sediment, the study authors reported.
“The mineralization we see in each egg is a very clear indication that it is a fossil structure,” Famoso said.
Because insect egg fossils are so rare, there aren’t many specimens available for comparison. So Lee consulted a global insect egg database of more than 6,700 living species to identify eggs in capsule fossils.
“I compared the defining characteristics of eggs, such as the size, aspect ratio and curvature of each egg, with those of live eggs,” he explains. “With the exception of grasshoppers and locusts, such large, oval-shaped, and large clutches of eggs (about 50 eggs in total) have not been seen in any other living insect group.”
The unusual discovery provides an unprecedented look at reproduction in an ancient relative of modern grasshoppers. Famoso added that this nearly pristine specimen also demonstrates the level of conservation of the national park’s fossil beds.
“Being able to see the interior and properly describe what it looks like is really exciting for us,” Famoso said. “As far as we know, there’s nothing like it in the fossil record.”
—Mindy Weisberger is a science writer and media producer whose work has appeared in Live Science, Scientific American, and How It Works magazine.