Green River Formation Cricket and Leaf Fossils

The Green River Formation deposits of Wyoming, Colorado, and Utah are best known for their immaculately-preserved fish, but other examples are known as well, as this specimen attests. The cricket is most likely Pronemobius sp, possibly P. smithii, and shows that there has been little change in these insects over the past 45 million years or so. There is also a fine leaf preserved in fine detail. This is an example of a leaf from a member of the Ulmaceae, or Elms. The closest living relative is Zelkova serrata which has strongly serrated leaf margins, and is a popular cultivated tree from Japan. The genus went extinct in North America during the Tertiary. This is a fine association plaque sure to become a prized addition to any Green River fossil collection.