The old view of sauropods, due to their girth and sheer size, was that of a swamp and marsh dwelling creature supporting its weight through buoyancy in the waters. Dragging its tail and sometimes snorkeling in the deep Jurassic waters, Apatosaurus was thought to be a slowly moving gentle giant capable only of outlasting predators by hiding in the murky depths. Charles Knight, and others, captured this wonderfully in their illustrations of sauropods like this Apatosaurus printed under the name of Brontosaurus. Three species of Apatosaurus are presently recognized as valid (Apatosaurus excelsus Marsh, 1879;Apatosaurus louisae Holland, 1915; andApatosaurus parvus Peterson and Gilmore, 1902). The average size of these monstrously large animals was around 75ft (23m) and estimates range between 16 and 35 tonnes in mass, making the original hypotheses of buoyancy for weight support much more logical; though obviously we know more now about the anatomical engineering marvel of sauropod vertebral columns and limbs.