Phreatoicidea is a suborder of isopod crustacean

Crustacean

Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s. Extant species are confined to freshwater

Fresh Water

Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...

 environments in South Africa

South Africa

The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

, India

India

India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

, and Oceania

Oceania

Oceania is a region centered on the islands of the tropical Pacific Ocean. Conceptions of what constitutes Oceania range from the coral atolls and volcanic islands of the South Pacific to the entire insular region between Asia and the Americas, including Australasia and the Malay Archipelago...

. This seemingly Gondwana

Gondwana

In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...

-derived distribution belies the fact that the group once had a cosmopolitan distribution

Cosmopolitan distribution

In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...

; fossils which can be assigned to the Phreatoicidea are the oldest isopod fossils, and are found throughout the world. In the intervening 325 million years, phreatoicideans have changed little, and are thus considered living fossil

Living fossil

Living fossil is an informal term for any living species which appears similar to a species otherwise only known from fossils and which has no close living relatives, or a group of organisms which have long fossil records...

s.

The first Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

n phreatoicidean was described by Charles Chilton

Charles Chilton (zoologist)

Charles Chilton was a New Zealand zoologist, the first rector to be appointed in Australasia, and the first person to be awarded a D.Sc. degree in New Zealand.-Biography:...

 in 1891. Two families are represented in Australia: Amphisopodidae in the interior of Australia, and in the west, and Phreatoicidae

Phreatoicidae

Phreatoicidae is a family of blind, freshwater isopods. They have survived apparently unchanged for 350 million years, and are only found in South Africa, India, Australia and New Zealand. They were first found near Christchurch in 1882 by Charles Chilton...

 in New South Wales

New South Wales

New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...

, Victoria

Victoria (Australia)

Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....

 and Tasmania

Tasmania

Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...

.