Still Swimming, Walking, and Flying 50 Million Years Later Fossil collections from Fossil Lake range from pollen spores and microscopic bacteria, to giant palm fronds and crocodiles up to 13-feet long. One unique aspect of the Fossil Butte locality is that it contains an entire ecosystem frozen in time, allowing us a rare glimpse of what life was like more than 50 million years ago. Although all of the Green River Formation species are now extinct, many of their relatives live on around the world. Relatives of the arowanas found throughout the Fossil Lake deposit, for instance, are now found only in the warm, tropical freshwaters of South America, Southeast Asia, and Australia. Other fishes, such as paddlefishes and gars, continue to live as distinct components of the North American fish fauna. You can see living arowanas, gars, and paddlefishes, as well as other modern-day relatives of fishes from Fossil Lake, at the Shedd Aquarium.