The beaver that ate Yellowstone

摘要

THE volcanic activity that shaped Yellowstone national park may have sculpted something on a much smaller scale too - the teetl of some rodents. Mountain beavers {Aplodontia rufa) have teeth with deep crown thick enamel and short roots -a condition called hypsodonty, typical of animals that chew gritty, silica-rich grasses. Yet they are partial to soft plants, so why the tough teeth?