Green River Fossils: Bats, Crayfish, Horse, Turtles.

The Green River Formation has yielded some of the best-preserved and oldest fossil bats ever discovered. It has also produced a remarkable variety of unusual fossils, including turtles, crayfish, horses, and stingrays. Many of these specimens come from Fossil Lake and are exceptionally detailed due to the fine-grained sediment in which they were preserved.

Fossil Turtles

One of the most impressive discoveries is a 1.7-meter (5 ft 6 in) softshell turtle, among the largest known from Fossil Lake. During the Eocene epoch, trionychid turtles reached their maximum size. Today, North America's largest softshell turtles grow only to about 51 cm (20 inches).

Another notable specimen belongs to the extinct Baenidae family. Shell features, a long tail, and recurved claws suggest these turtles were strong bottom-walkers that thrived in ancient lake environments.

Fossil Horses

Most mammal fossils consist of isolated teeth or bone fragments. However, the Green River Formation produced a fully articulated early horse—an extremely rare and significant discovery. To date, it remains the only horse found in the formation.

Fossil Stingrays

The stingray Heliobatis radians had small crushing teeth adapted for feeding on snails and mollusks. It also possessed barbed tail spines used for defense, showing that complex aquatic ecosystems thrived in Fossil Lake.

Fossil Crayfish

Crayfish lived in the shallow, near-shore waters of Fossil Lake. The genus Procambarus is known only from Eocene deposits of this region. Its closest living relative, Austrocambarus, is found in modern-day Mexico.

“Turritella” Agate

“Turritella Agate” is a brownish gemstone material containing fossil snail shells preserved within semitransparent chalcedony. The spiral shells accumulated in shallow inland sea sediments and were later agatized by silica deposition, creating a highly desirable lapidary material.

Although widely known as “Turritella,” the name is technically incorrect. The fossil snails preserved in this agate belong to the species Elimia tenera, a member of the Pleuroceridae family. A more accurate name would be “Elimia Agate.”