An even more impractical design shaped the skull of the pachycephalosaurid Dracorex hogwartsia—an intricate sunburst of spiky horns and knobs, without a dome. Only one such skull has been unearthed; it is on display, with the playful name derived from Harry Potter's school of witchcraft and wizardry, in Indianapolis's Children's Museum. Duck-billed Parasaurolophus walkeri, another late Cretaceous plant-eater, sported a spectacular pipelike structure, sweeping back from its skull, that was once theorized to act as a snorkel in swimming. But the tubular crest had no hole for gathering air. It may have served as a trumpeting noisemaker, for herd communication, or supported a bright flap of skin beguiling to a Parasaurolophus of the opposite gender. Sexual success and herd acceptance perpetuate genes as much as combative prowess and food-gathering ability.
Dinosaurs have always presented adaptive puzzles. How did huge herbivores like Brachiosaurus, Apatosaurus, and Diplodocus get enough daily food into their tiny mouths to fill their cavernous guts? Of the two familiar dinosaurs whose life-and-death struggle was memorably animated in Walt Disney's 1940 Fantasia (though in fact they never met in the corridors of time, failing to overlap by fully 75 million years), T. rex had puzzlingly tiny arms and Stegosaurus carried on its back a double row of huge bony plates negligible as defensive armor and problematic as heat controls. Not that biological features need to be efficient to be carried along. Some Darwinian purists don't even like the word "adaptive," as carrying a taint of implied teleology, of purposeful self-improvement. All that is certain is that dinosaur skeletons demonstrate the viability, for a time, of certain dimensions and conformations. Yet even Darwin, on the last page of The Origin of Species, in summing up his theory as "Natural Selection, entailing Divergence of Character and the Extinction of less-improved forms," lets fall a shadow of value judgment with the "less-improved."
In what sense are living forms improvements over the dinosaurs? All life-forms, even such long-lasting ones as blue-green algae and horseshoe crabs and crocodiles, will eventually flunk some test posed by environmental conditions and meet extinction. One can safely say that no dinosaur was as intelligent as Homo sapiens, or even as chimpanzees. And none that are known, not even a heavyweight champion like Argentinosaurus, was as big as a blue whale. One can believe that none was as beautiful in swift motion as a cheetah or an antelope, or as impressive to our mammalian aesthetic sense as a tiger. But beyond this it is hard to talk of improvement, especially since for all its fine qualities Homo sapiens is befouling the environment like no fauna before it.