The Evolutionary Journey of Crabs: From Sea to Land and Back

A new study has found that true crabs (Brachyura) have evolved to migrate from marine to land habitats between seven and 17 times over the past 100 million years. Some crabs even returned to the sea from land on two or three occasions. Most crabs are only able to survive in semi-terrestrial habitats, with land-based crabs concentrated in one species-rich group. The findings suggest that true crabs emerged about 45 million years earlier than previously estimated, dating back to the mid-Triassic period.