Tanzanonautes tuerkayi is a species of fossil freshwater crab from Tanzania, the only species in the genus Tanzanonautes.[1] It is the oldest known freshwater crab, and probably dates from the Oligocene;[1] [2] the next oldest specimens are from the Miocene.[1] A number of fragmentary remains were discovered in the Songwe Valley part of the East African Rift in Mbeya Region, Tanzania (approximately -8.93333333333333 0.2), in fragile sandstone sediments.[1] The animal had a carapace around across the widest part, which is around 15mm from the front of the carapace; the carapace is 44mm from front to back, and the slightly inward-curving rear edge of the carapace is 28mm across.[1] 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.[1] The genus Tanzanonautes is assigned to the family Potamonautidae, although the characters mentioned in the family's diagnosis are missing from the fragmentary fossils available.[1]