''Elimia tenera'' in chalcedony_from_Wyoming_.html" ;"title="Wyoming.html" ;"title="chalcedony from Wyoming">chalcedony from Wyoming ">Wyoming.html" ;"title="chalcedony from Wyoming">chalcedony from Wyoming ''Elimia tenera'', formerly known as ''Goniobasis tenera'', is an extinct species of freshwater snail with an operculum (gastropod), operculum, in the aquatic gastropod mollusk family Pleuroceridae. This species flourished during the Eocene and is now known only from the

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

record.

The genus name ''Elimia'' was restored to this species in 1975; formerly it was placed in ''

Goniobasis ''Pleurocera'' is a genus of freshwater snails with an operculum (gastropod), operculum, aquatic animal, aquatic gastropod mollusks in the family Pleuroceridae.Neubauer, Thomas A. (2014). Pleurocera Rafinesque, 1818. Accessed through: World Regis ...

''.

Green River Formation deposits

Fossilized ''Elimia tenera'' shells occur in a region which is now southern

Wyoming Wyoming () is a U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the south ...

, northern

Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...

and northeastern

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

. The best preserved ''Elimia tenera'' are from Lake Gosiute which fossils occur in the Fort Laclede Bed of the Laney Member at outcrops in Sweetwater County, in southwestern Wyoming.

'Turritella agate'

The fossils are hosted in

chalcedony Chalcedony ( , or ) is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monoclinic. ...

rich sedimentary rock. This rock was originally incorrectly called ''Turritella agate''. It was named after the sea snail genus ''

Turritella ''Turritella'' is a genus of medium-sized sea snails with an operculum, marine gastropod mollusks in the family Turritellidae.Vos, C.; Gofas, S. (2013). Turritella Lamarck, 1799. Accessed through: World Register of Marine Species at http://www. ...

'' because of the resemblance of the freshwater snail shells to the ''Turritella'' fossils that are found in

agate Agate () is a common rock formation, consisting of chalcedony and quartz as its primary components, with a wide variety of colors. Agates are primarily formed within volcanic and metamorphic rocks. The ornamental use of agate was common in Ancie ...

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

and

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

. The Wyoming fossil shells, however, are in a freshwater sedimentary deposit and identifiable as the genus ''Elimia'', and are less-silicified than those in Texas and California.

Paleoecology and paleogeology

The fossil beds are approximately 46 to 51 million years old and occur in the Laney Member of the

Green River Formation The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes in three basins along the present-day Green River in Colorado, Wyoming, and Utah. The sediments are deposited in very fine ...

. Evidence suggests that the ''Elimia tenera'' were deposited nearshore in a series of shallow lakes, which geologists have named the Fossil, Uinta and Gosiute Lakes. The climate was subtropical and there were intermittent volcanic eruptions.Carroll, A. R. & Bohacs, K. M. (1999). "Stratigraphic classification of ancient lakes: Balancing tectonic and climatic controls". ''Geology''. 27: pp. 99-102

References

External links

Allmon, Warren D. "Turritella Agate"
Museum of the Earth {{DEFAULTSORT:Elimia Tenera Elimia Eocene gastropods Gastropods described in 1845 Fossil taxa described in 1845