Word History Take a little deception, add a little excitement, stir them with a century-long mistake, and you have the mystery of the brontosaurus. Specifically, you have the mystery of its name. For 100 years this 70-foot-long, 30-ton vegetarian giant had two names. This case of double identity began in 1877, when bones of a large dinosaur were discovered. The creature was dubbed apatosaurus, a name that meant “deceptive lizard” or “unreal lizard.” Two years later, bones of a larger dinosaur were found, and in all the excitement, scientists named it brontosaurus or “thunder lizard.” This name stuck until scientists decided it was all a mistake—the two sets of bones actually belonged to the same type of dinosaur. Since it is a rule in taxonomy that the first name given to a newly discovered organism is the one that must be used, scientists have had to use the term apatosaurus. But “thunder lizard” had found a lot of popular appeal, and many people still prefer to call the beast brontosaurus.