malacostracan

The shape and complexity is roughly corresponding to that of a modern malacostracan brain.

Mysida is a group of small, shrimp-like crustaceans, an order in the malacostracan superorder Peracarida.

Decapod-like gills suggest malacostracan affinities.

Some people call the horseshoe crab a "helmet crab", but this common name is more frequently applied to a true crab, a malacostracan, of the species Telmessus cheiragonus.

This characteristic, which is shared with malacostracan groups such as the Decapoda and Euphausiacea (krill) has been used to suggest a link between Remipedia and Malacostraca.

This group is believed to be the most primitive malacostracan group, because they lack some of the caridoid facies, such as the presence of seven abdominal segments (eight if telson is included).

The other major malacostracan superorder, the Peracarida, is highly diverse in habit, size and shape and contains 21,500 species, but this number is a gross underestimate as the number of described species has tripled in the past 20 years.

In 1909, he wrote the Crustacea section in Lankester's Treatise on Zoology, where he introduced the superorders Eucarida, Peracarida and Hoplocarida as well as the concept of the caridoid facies, a hypothetical ancestral malacostracan.