''Allocrangonyx'' is a genus of

troglobitic A troglobite (or, formally, troglobiont) is an animal species, or population of a species, strictly bound to underground habitats, such as caves. These are separate from species that mainly live in above-ground habitats but are also able to live u ...

amphipod Amphipoda () is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods () range in size from and are mostly detritivores or scavengers. There are more than 10,700 amphipod species cur ...

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s from the

South Central United States The West South Central states, colloquially known as the South Central states, is a region of the United States defined by the U.S. Census Bureau as covering four states: Arkansas, Louisiana, Oklahoma, and Texas. The West South Central or Sou ...

. The two species are both listed as vulnerable on the

IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is an inventory of the global conservation status and extinction risk of biological ...

. The animals are blind and unpigmented. During the male's development, the outer ramus of the third

uropod Uropods are posterior appendages found on a wide variety of crustaceans. They typically have functions in locomotion. Definition Uropods are often defined as the appendages of the last body segment of a crustacean. An alternative definition sugge ...

differentiates into secondary segments and grows to a length greater than the animal's body length. Turner falls ok

''Allocrangonyx pellucidus''

''A. pellucidus'', the "Oklahoma cave amphipod", is known from caves and springs in the

Arbuckle Mountains The Arbuckle Mountains are an ancient mountain range in south-central Oklahoma in the United States. They lie in Murray County, Oklahoma, Murray, Carter County, Oklahoma, Carter, Pontotoc County, Oklahoma, Pontotoc, and Johnston County, Oklahoma, ...

of Johnston,

Murray Murray may refer to: Businesses * Murray (bicycle company), an American bicycle manufacturer * Murray Motor Car Company, an American car manufacturer * Murrays, an Australian bus company * Murray International Trust, a Scottish investment trus ...

and Pontotoc counties,

Oklahoma Oklahoma ( ; Choctaw language, Choctaw: , ) is a landlocked U.S. state, state in the South Central United States, South Central region of the United States. It borders Texas to the south and west, Kansas to the north, Missouri to the northea ...

. The largest males reach long, while females reach .

''Allocrangonyx hubrichti''

''A. hubrichti'', the "Central Missouri cave amphipod" or "Hubricht's long-tailed amphipod", was thought for many years to be

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to the state of

Missouri Missouri (''see #Etymology and pronunciation, pronunciation'') is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. Ranking List of U.S. states and territories by area, 21st in land area, it border ...

, but specimens were discovered in 1996, away, in a

water well A well is an excavation or structure created on the earth by digging, driving, or drilling to access liquid resources, usually water. The oldest and most common kind of well is a water well, to access groundwater in underground aquifers. The ...

near

Romance Romance may refer to: Common meanings * Romance (love), emotional attraction towards another person and the courtship behaviors undertaken to express the feelings ** Romantic orientation, the classification of the sex or gender with which a pers ...

, White County,

Arkansas Arkansas ( ) is a landlocked state in the West South Central region of the Southern United States. It borders Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, Texas to the southwest, and Oklahoma ...

. While the well is drilled into

Pennsylvanian Pennsylvanian may refer to: * A person or thing from Pennsylvania * Pennsylvanian (geology) The Pennsylvanian ( , also known as Upper Carboniferous or Late Carboniferous) is, on the International Commission on Stratigraphy, ICS geologic timesc ...

age

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

, all previous records have been from

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ...

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

s and dolomites.

References

{{Authority control Gammarida Amphipod genera Crustaceans of the United States Freshwater crustaceans of North America Taxonomy articles created by Polbot Cave crustaceans