Among the most enduring assumptions in paleontology was that the largest creatures ever to walk the Earth must have bred close to the warmth of the equator. New fossil evidence from cold Mesozoic regions of the Southern Hemisphere has quietly dismantled that certainty, revealing that giant sauropod dinosaurs nested far from the tropics and, unable to sit upon their eggs without crushing them, likely entrusted the work of incubation to the slow heat of decomposing vegetation. In doing so, these animals remind us that life's ingenuity in the face of physical constraint has always exceeded our ex