Tags: Crustacean.
Eumalacostraca is a subclass of crustaceans containing almost all living malacostracans or about 40000 described species. The remaining subclasses are the Phyllocarida and possibly the Hoplocarida. Eumalacostracans have 19 segments (5 cephalic 8 thoracic and 6 abdominal). The thoracic limbs are jointed and used for swimming or walking. The common ancestor is thought to have had a carapace and most living species possess one but it has been lost in some subgroups.
