The Green River stretches 730 miles (10+02) across Wyoming, Utah and Colorado. Its average yearly mean flow is 6,121 cubic feet per second (10+03), which is 193 billion cubic feet per year (10+11). Sediments from Green River Formation date back to the Eocene Epoch (roughly 55 – 34 million or 10+07 years ago), making it a key fossil site for understanding the Eocene period.
According to the University of California Museum of Paleontology, “The Green River Formation is the site at which the fossil of the oldest known flying mammal was found. This organism, a bat, Icaronycteris index, was preserved with its skeleton, membranes and cartilage intact. It was discovered along with food still inside its body and waste not yet disposed, so some of the flora, algae, pollen and arthropods of the time can be studied. It is rare that a complete fossil is found, and this makes the bat fossil very useful for paleontologists to study.”
In addition to the oldest known flying mammal, Green River fossils have revealed approximately 60 vertebrate taxa (including fish, reptiles, birds and mammals), as well as eleven species of reptiles. To learn more, click here.