460 MICROFOSSILS/Ostracoda Figure Stratigraphical time lines of the major ecological radiations of the Ostracoda In the Silurian, some palaeocopids (Figure 8), platycopids, and leperditicopids may have begun to adapt to marginal marine, brackish water (and perhaps hypersaline) conditions; diverse palaeocopids dominated shallow marine shelf waters, giving way to ‘non-palaeocope’ faunas (including metacopines) in deeper water The Ordovician–Devonian leperditicopids include the largest known ostracods (up to 50 mm long) and inhabited marginal marine environments, including tidal flats and estuaries, possibly entering freshwater environments in the Devonian; it has been speculated that they occupy an ancestral