Two tiny ant fossils found in southern Saskatchewan are offering scientists new clues about how modern ants evolved. These fossils, which are between 72 and 56 million years old, are rare examples of ants from that time period. Researchers, including Elyssa Loewen, Caelan Libke, and Dr. Ryan McKellar, studied the fossils using the Canadian Light Source (CLS), a facility at the University of Saskatchewan that uses powerful X-rays to examine small objects in detail. The fossils were discovered in the Big Muddy amber deposit, a site known for preserving insects, plants, and other traces of ancient environments from a swampy forest. To analyze the fossils, the amber containing the ants was first embedded in epoxy and polished to reveal the insects inside. Then, the samples were scanned using ultrabright X-ray micro-tomography, a technique that creates 3D models of the ants' anatomy without damaging them. By comparing these models with modern ant species, the researchers were able to identify the fossils as belonging to specific ant subfamilies that are still found today. These ant groups were once widespread in North America but are now mostly located in the global south. Using a machine-learning model developed by Dr. Christine Sosiak, the team made predictions about how these ancient ants may have lived. They believe the partial ant head fossil belonged to a group that lived on the ground around 67 million years ago. In contrast, ants from the same family that appeared after the extinction of the non-avian dinosaurs lived in trees, similar to many modern ant species. This suggests an evolutionary shift from living on the forest floor to inhabiting the canopy. At that time, the Big Muddy region was a lush, swampy forest filled with ancient trees, ferns, and flowering plants. These ants coexisted with a wide variety of insects just one million years before the end-Cretaceous mass extinction, which marked the end of the age of the dinosaurs. Loewen points out that ants play a crucial role in shaping ecosystems, and understanding how they adapted after the extinction of the non-avian dinosaurs helps scientists understand how today's ecosystems developed. The amber samples are now preserved at the Royal Saskatchewan Museum and are available for future research. Loewen, who currently works as a collection technician at the Canadian Museum of Nature in Ottawa, hopes to continue exploring the Big Muddy deposit for more fossils that could provide further insights into the evolution of insects in North America.