Lemurs are a clade of strepsirrhine primates endemic to the island of Madagascar. Lemurs arrived in Madagascar around 62 to 65 mya by rafting on mats of vegetation at a time when ocean currents favored oceanic dispersal to the island. Ranging in size from 30 g (1.1 oz) to 9 kg (20 lb), lemurs share many common, basal primate traits, such as divergent digits on their hands and feet and nails instead of claws (in most species). However, their brain-to-body size ratio is smaller than that of anthropoid primates. Since that time, lemurs have evolved to cope with an extremely seasonal environment and their adaptations give them a level of diversity that rivals that of all other primate groups.