Ants help scientists discover thousands of fossils

Ancient mammals described by the Rochester Institute of Vertebrate Paleontology in research published in May in the journal Paludicola include the lighter-than-bulb kangaroo, a relative of the beaver. mountains and ancestors of kangaroo rats. The study revealed the diversity of mammals in North America about 33-35 million years ago, when the climate changed drastically. The scientists also noted the contribution of insects that specialize in collecting fossils, creating a long-term collaboration between the team of paleontologists and the reaper.

The reaping ant is likened to an effective assistant of paleontologists.

"The reaping ants aren't great at burning you," says Samantha Hopkins, professor of earth science at the University of Oregon. "But I'm very grateful to them because they make my job so much easier."

Most reaping ants live in underground burrows, located below mounds of earth. Harvester ants reinforce these mounds by using pieces of rock and other hard material to cover them. They can crawl up to 30 m from the burrow and dig 1.8 m deep to find materials to help protect the mound. That material includes fossils, particularly in the badlands of Wyoming, Nebraska and South Dakota, where fossils are abundant and can be found in loose soil. Harvester ants can carry materials 10 to 50 times their body weight. The heaviest fossil they could collect was lighter than the average pill.

Due to this size limit, the mounds of reaping ants are ideal places to find microfossils, animal fossils too small to see without a microscope. For more than a century, scientists like Dr. Hopkins have been scraping sediment from the mound walls of reaping ants in search of this fossil, from which it is easy to find large numbers of mammal teeth without losing any of them. many hours sifting soil and sand in the field.

In 2015, an amateur fossil hunter in Sioux County in northwestern Nebraska noticed a large number of fossil teeth and jawbones lying above an ant nest in his home. This person sent the specimen to Clint Boyd, a paleontologist at the North Dakota Geological Survey. Over the years, samples kept coming in. By 2020, Dr. Boyd had more than 6,000 identifiable specimens. With the help of Bill Korth, research assistant at the Rochester Museum and Science Center in New York, and several other paleontologists, Dr. Boyd was able to identify dozens of species in the collection, as well as 10 new species.

These new species include Cedromus modicus, a relative of modern squirrels that lasted only a few million years, and Yoderimys massarae, the smallest member of the extinct family Eomyidae. In particular, the relative of the beaver, Costepeiromys attasorus, was named in honor of the reaper ant that discovered the fossil.

Based on the location and age of the rock layer surrounding the ant nest, the researchers estimate the fossils come from the late Thuy Tan and early Tien Tan epochs. During that period, the Earth's climate cooled considerably. Understanding how diverse mammals were during and after this period will help researchers predict how mammals today will respond to climate change.