Chaetoceros is probably the largest genus of marine planktonic diatoms with approximately 400 species described. Although a large number of these descriptions are no longer valid. It is often very difficult to distinguish between different Chaetocerosspecies.^[1] Several attempts have been made to restructure this large genus into subgenera and this work is still in progress^[2][3]However, most of the effort to describe species have been focused in boreal areas, and the genus is cosmopolitan, so there are probably a large number of tropical species still undescribed.^[4]

(From Wikipedia, May 31st, 2012)