Over millions of years, Australia's unique biodiversity has produced a large cabinet of curiosities. Among the weirder members of this group were the Mihirungs, members of the now extinct family Dromornithidae. Made up of several genera of flightless birds--among them one of the very largest birds that ever lived--the dromornithids ranged from 60-kilogram beasts, 1.5 meters tall, to giants twice that size, weighing nearly half a metric ton. They...