Diastylidae have a medium to large, free
telson, that has not fused with the last
pleon segment. The telson usually bears two terminal
setae. Males have generally two pairs of
pleopods, though in rare cases they may be rather small or even entirely absent. The flagellum of the second antenna reaches past the
pereon. In females the second antenna is much smaller than the first antenna. In males the third
maxilliped and the first four
pereiopods almost always have
exopods (outer branches). In females they may, in rare cases, be absent from all but the third maxillipeds, and the two first pereiopods. The interior branch of the
uropods are generally made up of two or three segments, but in some rare case may have just one. Members of this family frequently show clear
sexual dimorphism. ==Genera==