In 1879, Othiniel Charles Marsh announced a new species of sauropod, known as "Brontosaurus excelsus," and presented as proof a complete skeleton made up of bones from different kinds of actual, real sauropods. This was in an age when dinosaur discoveries were terrifically popular events, and Brontosaurus - an easy-to-pronounce, aesthetically pleasing vegetarian dinosaur - quickly become a public favorite. Despite a 1903 re-examination that revealed that the fossils were not from a new species at all, the name "Brontosaurus" has been a part of dinosaur nomenclature ever since, grudgingly accepted as an informal synonym for the Apatosaurus species.
It is with much teeth-grinding that I must report that, in the process of typing this, Google Chrome insists that "Apatosaurus" is not a properly-spelled word, and suggests Brontosaurus as a replacement.
The original picture that this design is based on was drawn by me sometime when I was 4-7 years old. I've recently rediscovered it, touched it up, and made it available here.