Large creatures have a tendency to shrink when trapped in small areas with limited resources. Half-size Malagasy hippos, 20-inch-tall goats, pony-size elephants, and 3-foot-tall humans on the Indonesian island of Flores are examples of "island dwarfism."
Even sauropods, the largest creatures ever to walk the earth, were subject to shrinking. University of Bonn paleontologist Martin Sander analyzed growth rings in presumed juvenile bones from the sauropod Europasaurus holgeri. Rather than being spaced out, as is typical of younger animals, the marks were tightly compressed, like a normal adult's. "It's the first proven record of dwarfism in dinosaurs," Sanders says. It also makes Germany home to the earliest example of island dwarfism, but that's not as strange as it sounds. One hundred and fifty million years ago, parts of Germany were mostly underwater. E. holgeri's larger ancestors probably waded out to an island, were trapped by rising sea levels, and shrank to survive.