Higher crustaceans of distinctly modern type first diversified in the Lower Carboniferous. Some, from Scottish and Northern English localities, are exquisitely preserved, so that much can be inferred about their biology. Yet they seem to have been environmentally restricted, confined to close inshore marine fades and to lagoons and ponds of reduced, salinity. For all their apparent modernity, no Carboniferous crustaceans ever developed pincer–like claws, so common in modern types. Might this have been one of the factors that limited the