Tanzanonautes tuerkayi is a species of fossil

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 freshwater crab

Freshwater crab

There are around 1,300 species of freshwater crabs, distributed throughout the tropics and subtropics, divided among eight families. They show direct development and maternal care of a small number of offspring, in contrast to marine crabs which release thousands of planktonic larvae. This limits...

 from Tanzania

Tanzania

The United Republic of Tanzania is a country in East Africa bordered by Kenya and Uganda to the north, Rwanda, Burundi, and the Democratic Republic of the Congo to the west, and Zambia, Malawi, and Mozambique to the south. The country's eastern borders lie on the Indian Ocean.Tanzania is a state...

, the only species in the genus Tanzanonautes. It is the oldest known freshwater crab, and probably dates from the Oligocene

Oligocene

The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...

; the next oldest specimens are from the Miocene

Miocene

The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...

. A number of fragmentary remains were discovered in the Songwe Valley part of the East African Rift

East African Rift

The East African Rift is an active continental rift zone in eastern Africa that appears to be a developing divergent tectonic plate boundary. It is part of the larger Great Rift Valley. The rift is a narrow zone in which the African Plate is in the process of splitting into two new tectonic plates...

 in Mbeya Region

Mbeya Region

Mbeya is one of Tanzania's 26 administrative regions. The regional capital is Mbeya. It is bordered to the northwest by Tabora Region, to the northeast by Singida Region, to the East by Iringa Region, to the South by Zambia and Malawi and to the West by Rukwa Region...

, Tanzania (approximately ), in fragile sandstone

Sandstone

Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...

 sediments. The animal had a carapace

Carapace

A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...

 around 50 millimetres (2 in) across the widest part, which is around 15 mm (0.590551181102362 in) from the front of the carapace; the carapace is 44 mm (1.7 in) from front to back, and the slightly inward-curving rear edge of the carapace is 28 mm (1.1 in) across. The genus name refers to Tanzania, the country where the fossil was found, while the specific epithet commemorates Michael Türkay, an authority on freshwater crabs. The genus Tanzanonautes is assigned to the family Potamonautidae

Potamonautidae

Potamonautidae is a family of freshwater crabs endemic to tropical parts of Africa and adjacent islands, including Madagascar, the Seychelles, Zanzibar, Mafia, Pemba, Bioko, São Tomé, Príncipe and Sherbro Island. It comprises 18 extant genera and 138 extant species...

, although the characters mentioned in the family's diagnosis are missing from the fragmentary fossils available.