Monotypic prehistoric crustacean genera

Dexteria floridana is an extinct species of fairy shrimp in the family Chirocephalidae, the only species in the genus Dexteria. It was endemic to Florida, where it was known from a single pool, south of Gainesville. It was originally described by Ralph W. Dexter in 1953 as a species of Eubranchipus. The species was declared extinct on October 5, 2011 because it was found that the only known pool of water that contained the known population was filled in for development, thereby killing the shrimps.

Hymenocaris is a genus of Cambrian marine arthropod. The type species, Hymenocaris vermicaudata is known from the Upper Cambrian (Furongian) Ffestiniog Formation, in North Wales, United Kingdom.

Dollocaris is an extinct genus of thylacocephalan that lived during the Jurassic period. Fossils have been found in France, specifically the La Voulte-sur-Rhône lagerstätte. It is known for its massive compound eyes, giving Dollocaris a rather characteristic appearance. One species is currently known, D. ingens.

Ainiktozoon loganense ("Logan's enigmatic animal", from (aíniktós, "riddling, enigmatical"), living thing), is a fossil arthropod from the Silurian of Scotland.