Coastlines can look like simple lines on a map. Over Earth’s history, they acted more like gates and traps. A new study led by researchers at the University of Oxford suggests that the shape and direction of coastlines helped decide which shallow-sea animals survived, and which vanished, across the last 540 million years. The study links extinction risk to a detail you might overlook: whether a coastline runs mostly north to south, or east to west. The team reports that marine invertebrates living along convoluted coastlines, or coastlines that stretch east to west, faced higher odds of extinction than those living along north to south coasts. That pattern matters because coastlines can either help you move with changing temperatures, or block your escape. When the climate shifts, the ability to migrate toward cooler or warmer waters can decide survival. The new results suggest many species did not die out only because conditions worsened; many disappeared because geography limited their options. The relationship between coastline geometry and dispersal potential. (CREDIT: Science) A Fossil Record With a …