Imagine a crew of hungry toddlers and kindergartners with unrestricted access to the kitchen. Would they gorge themselves on candy, chips and ice cream? For a type of fast-growing youngster that lived 150 million years ago, the answer instead was a diverse, nutritious diet, rich in tender greens. That finding resulted from the discovery, announced Thursday, of a rare juvenile dinosaur skull belonging to one of those familiar, long-necked plant-eaters called sauropods.