Syncarida are shrimp-like crustaceans without a carapace. The body is divided into a 5-segmented head, a 7-8 segmented thorax and a 6-segmented abdomen. The antennules and antennae are moderately long. The antennules are biramous with both branches linear, the antennal expodites are scale-like. Some or all thoracic appendages are biramous. Unlike in the other malacostracan orders Decapoda, Amphipoda and Isopoda, the foremost thoracic legs are never modified as gnathopods. The abdomen may or may not carry leg-like appendages as long as those on the thorax.

There are two extant orders, Anaspidacea and Bathynellacea. Anaspidacea comprises two families (Anaspididae, Koonungidae) with moderate-sized benthic or hypogean species, and two families (Psammaspididae, Stygocarididae) of mainly smaller, hypogean to interstitial species. The geographic range of this order is restricted to south-eastern Australia, South America, and New Zealand.

In Australia, the family Anaspididae occurs in Tasmania and family Koonungidae in Victoria and Tasmania. The other two families are known from these two states and from the New England Tablelands of NSW.

The order Bathynellacea (Parabathynellidae, Bathynellidae), which is scarce but cosmopolitan, is entirely composed of small, blind crustaceans which live underground.