Diplomystus (skeleton)

Description

Diplomystus is an extinct genus of freshwater clupeomorph fish distantly related to modern-day extant herrings, alewives, and sardines. Their strongly upturned mouths suggest they fed in open water rather than feeding off the bottom. This specimen comes from the Green River Formation from the Warfield Springs Quarry near Thayne, Wyoming. The Green River Formation is a famous package of rock that was deposited by a large lake system found in Wyoming, Colorado, and Utah during the Eocene (56 to 33.9 million years ago). The Green River Formation has produced many spectacular fossils, including many different types of fish, rays, insects, plants, and mammals. Diplomystus is a common fossil in the formation.