Anostracans, fairy and brine shrimps, differ from other large branchiopods in having stalked compound eyes and in not having any shield covering the body. Their external morphology has not changed since the Jurassic. Fairy shrimps are backstrokers, their ventral side is oriented to the light. Setae of the ventral groove transport the nutritive pulp to the mouth. Adult females have an ovisac where the mature eggs are continuously moved to be supplied with oxygene.
Adult males show prominent antennar appendages used for clasping the females during pairing.
Tadpole shrimps usually live near the ground of astatic pools, where they move with their ventral side down. Notostracans sometimes even cannibalize freshly moulted members of the same species. In Northern and Central Europe, with few exceptions all tadpole shrimps are female, whereas sex ratios in Southern and Western Europe as well as in Northern Africa are near unity. Modified appendages of the 11th pair of limbs bear the ovisacs with the mature eggs. Conchostracans are the oldest recent group among the large branchiopods and are known since the Silurian.