Eocene Green River Grasshopper IF-PCM-16-094

Pronemobius smithii (Scudder)
Green River Formation
Parachute Creek Member
Middle Eocene
Uintah County, Utah

Here is a good specimen of the grasshopper family Orthoptera. The head, thorax and abdomen are very well preserved.  Several legs are present.  The wings are absent. 
The name Orthoptera is sometimes used for all the insects in the "orthopteroid" assemblage, including roaches, earwigs, mantises, and many others. However, it is more usual to restrict the Orthoptera (Greek for "straight-wing") to the crickets, grasshoppers, katydids, and their kin. These insects are instantly recognizable by their long hind legs, which are modified for jumping. Most orthopterans can generate noise by rubbing special organs together on their legs or on their wings, a habit known as stridulation. 

The upper part of the Green River Formation in the eastern Uinta Basin is present in two stratigraphic intervals separated by approximately 250 m of sandstone, siltstone, marlstone and lacustrine limestone (micrite, boundstone, grainstone).  The lower sequence, in the Garden Gulch Member, represents an early lacustrine phase of Lake Uinta and consists of approximately 29 m of interbedded clay-rich oil shale, gastropod grainstone and packstone, ostracode grainstone, algal boundstone and calcareous silty claystone. Fish fossils, plant debris, and pelecypods are locally present. Detrital clay minerals (smectite, chlorite and illite) are common and calcite abundance is greater than dolomite. The second oil-shale interval is located in the upper 10 m of the Parachute Creek Member. The Mahogany ledge crops out in the lower 15 m of this sequence. Oil shale in the Parachute Creek Member is a kerogenous dolomicrite (dolomite greater than calcite). Analcime, quartz, K-feldspar, and albite are also common. Illite is the dominant clay mineral. Fossils include insects, insect larvae, and plant debris. Marlstone and volcanic tuff are interstratified with oil shale.