Discovering an Ancient Swamp Dweller: A New Mammal from Colorado's Past

Stepping back in time to the age of dinosaurs. In Colorado, paleontologists have found the fossils of a new mammal species that lived around 70 to 75 million years ago. This creature, named Heleocola piceanus, was an opossum-like animal related to today's marsupials. The discovery is exciting because it fills a gap in our knowledge about mammals from this period. The fossils were found near Rangely in northwest Colorado. They included a piece of jawbone and three molar teeth. The name Heleocola means "swamp dweller" in Latin, hinting at the creature's possible habitat. During this time, a vast inland sea called the Western Interior Seaway divided North America into two landmasses, Laramidia and Appalachia. Much of eastern Colorado was underwater, while the western part was likely swampy. The region where the new species was found was where land met water, creating a unique environment. This area was home to various creatures, including turtles, duck-billed dinosaurs, and giant crocodiles. Heleocola piceanus was larger than most mammals of its time. While today's mammals of similar size might include mice or rats, Heleocola was more like a muskrat. This discovery challenges our previous understanding that all mammals from this period were small. "There are a few animals from the Late Cretaceous that are bigger than we expected, " Jaelyn Eberle, the lead researcher from the University of Colorado Boulder, explained.