Diastylidae is one of the eight most commonly recognised families of crustaceans of the order Cumacea. They are marine creatures especially common around the 30th parallel north.
Anatomy
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 There are around 285 species, in 24 genera:
Anchicolurus Stebbing, 1912 Anchistylis Hole, 1945 Atlantistylis Reyss, 1975 Brachydiastylis Stebbing, 1912 Colurostylis Calman, 1911 Cuma Milne-Edwards, 1828 Diastylis Say, 1818 Diastyloides G. O. Sars, 1900 Diastylopsis Smith, 1880 Dic Stebbing, 1910 Dimorphostylis Zimmer, 1921 Divacuma Ekleptostylis Stebbing, 1912 Ektonodiastylis Gerken, Watling & Klitgaard, 2000 Geyserius Holostylis Stebbing, 1912 Leptostylis G. O. Sars, 1869 Leptostyloides Makrokylindrus Stebbing, 1912 Oxyurostylis Calman, 1912 Pachystylis Hansen, 1895 Paradiastylis Calman, 1904 Paraleptostylis Vassilenko, 1990 Vemakylindrus Bacescu, 1961
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