People once called this 70-foot-long plant eater Brontosaurus.  Then scientists, who thought a Brontosaurus and an Apatosaurus were two different species, discovered the two dinosaurs were actually the same.  So scientist applied the name first given to this huge, 33-ton dinosaur:  Apatosaurus.  The big animal had nostrils on top of its head, allowing it to breathe while part of its head was under water.