Sauropods were humongous creatures, but how  they got so large is a mystery that paleontologists are still trying to  unravel          
      Argentinosaurus and Futalognkosaurus, pictured, from prehistoric South America, stretched more than 100 feet long and weighed in excess of 70 tons.
Argentinosaurus and Futalognkosaurus, pictured, from prehistoric South America, stretched more than 100 feet long and weighed in excess of 70 tons. They were the most gigantic animals ever to walk the earth. Sauropod  dinosaurs—“thin at one end; much, much thicker in the middle; and then  thin again at the far end,” as comedian John Cleese described them—were  titans that thrived for more than 130 million years. The largest known  species, such as Argentinosaurus and Futalognkosaurus  from prehistoric South America, stretched more than 100 feet long and  weighed in excess of 70 tons. Bones found in the 1870s (and since  somehow lost) hint that an enigmatic species dubbed Amphicoelias may have been even bigger still.
 No land mammal has ever come close to the size of these gargantuan dinosaurs. The prehistoric hornless rhino Paraceratherium—the  largest land mammal ever—was a mere 40 feet long and weighed a paltry  17 tons, and today’s African bush elephants, at 5 tons, would look  dainty next to the largest sauropod dinosaurs. (Blue whales, at 100 feet  and 200 tons, are a bit more massive than sauropods, but it’s easier,  physiologically, to be large in an aquatic environment.)
 What was it about these dinosaurs that allowed them to become the biggest terrestrial animals of all time?