This arrangement is known as the "caridoid facies", a term coined by William Thomas Calman in 1909.

The common ancestor is thought to have had a carapace, and most living species possess one, but it has been lost in some subgroups.

Calman identified the following features as distinguishing eumalacostracan crustaceans:[3] "Carapace enveloping the thoracic region; movably stalked eyes; biramous first antenna; scale-like exopod on the second antenna; natatory exopods on the thoracic limbs; elongate, ventrally flexible abdomen; tail fan formed by the lamellar rami of the uropods on either side of the telson.

[2] The group as originally described by Karl Grobben[4] included the Stomatopoda (mantis shrimp), and a number of modern experts and databases (ex.

Subclass Eumalacostraca Grobben, 1892 This Malacostraca related article is a stub.