Derptile 8- The Sauropod.  Sauropods are most notable for their size.  Despite their mass, Paleontologists believe that because of the many air sacs in their bodies, sauropods would have extreme buoyancy in water.  The unique species, Derplodocus, pictured here, however, had air sacs only in its belly, leading scientists to believe it would float upside-down, submerging its head and drowning, which would explain their quick extinction.