Aspect of primitive Eumalacostraca distinguished by enclosure of thorax by carapace, movably stalked eyes, biramous antennules, scaphocerite-bearing antennae, thoracopods with natatory exopods, elongate abdomen ventrally flexed and powerfully muscled, and caudal fan [Moore and McCormick, 1969].
Basic group of characters distinguishing eumalacostracan crustaceans: enclosure of thorax by carapce, movable stalked eye, biramous antennules, antennae with scaphocerites, thoracopods with natatory exopods, ventrally flexed abdomen, and tailfan [McLaughlin, 1980].
Crustacea glossary. Natural History Museum of Los Angeles County. 2011.