A new species of proto-amphibian has been discovered and named by two students in honor of their mothers. Around 309 million years ago, the area that is now Chicago was a swampy river delta teeming with early land animals, giant insects, and strange aquatic creatures. Today, this region is home to one of the world's richest Carboniferous period fossil deposits. Two student scientists from the Field Museum have described the latest addition to this collection—a new species named Jeanerpeton mazonensis, which means "Jean's crawler from Mazon Creek." The species is an early ancestor of modern amphibians, resembling a squat and chubby salamander. The Mazon Creek area, which was once a river delta during the Carboniferous period, provided ideal conditions for fossilization. Sediment quickly covered dead animals and plants, preserving even soft tissues and fine details that are typically lost in the fossilization process. Today, Mazon Creek is renowned for its exceptional fossils, including features like toe pads and body outlines. "What's really cool about Mazon Creek is that it preserves all of these unusual details—things like toe pads and body outlines," said Allison Sefcovic, one of the study's co-lead authors and a 2025 Women in Science intern at the Field Museum. "In the fossil of Jeanerpeton, we can see some of the scales on its back and tiny 'belly ribs' called gastralia. You can even see the eye impressions! It's so cool to see." The fossil of Jeanerpeton mazonensis was originally found by an amateur collector and later donated to the Field Museum. At first glance, it was classified as another species, Amphibamus grandiceps, which is a well-known species from the region. However, poorly understood specimens are sometimes grouped into what scientists call a "waste bin taxon"—a metaphorical dumping ground for specimens that appear related but have not been thoroughly studied. "What we're finding from the Field Museum's collection are a bunch of things that historically were grouped together into this waste bin taxon known as Amphibamus grandiceps," said Cam So, a co-author of the study and postdoctoral researcher at the Field Museum. "Jeanerpeton is one of those species. And now, we've found enough evidence to support it being an anatomically distinct animal. With this publication, we officially pull Jeanerpeton out of this waste bin taxon." The study's co-lead authors, Payton Kohlberg and Sefcovic, were part of last year's cohort of Women in Science Interns at the Field Museum, a program designed to encourage young women to pursue careers in science and museums. They, along with So, are part of the lab group of Arjan Mann, the Field's assistant curator of fossil fishes and early tetrapods in the Negaunee Integrative Research Center. "Before working in the Mann Lab, I didn't know much about paleontology," said Kohlberg. "My experience at the Field and in the Women in Science program has made me more confident in my abilities to try something new. It is scary to take on a project when you feel like you don't know as much as you should, but I learned through practical experience that it is possible to overcome that fear with hard work." The discovery of Jeanerpeton mazonensis opens new avenues for researchers studying the biodiversity of the Mazon Creek area. These findings contribute to a detailed understanding of what life was like in Illinois over 300 million years ago, revealing a rich and complex ecosystem that once thrived in this region.