Soapberry plants are typically found in the tropics and their presence in a northerly latitude like where NE Utah is indicates that the climate used to be much warmer than it is now. Below is a leaf from the Soapberry family, called Cardiospermum coloradensis, that is also called "Balloon Vine". Fossils of these leaves are somewhat common in the Parachute Creek member of the Green River formation (Eocene, Lutetian stage), but most of what I have found are smaller. I purchased this piece because of the good preservation and size of the leaf. I identified it based on this image from James St. John's Flickr page.