The wingspan of the largest species of pteranodon (the term employed by working paleontologists as opposed to the culturally popular term "pterodactyl") was up to 30 feet. This wingspan is much larger than that of any modern flying bird.
About.com states that it is unclear when "pterodactyl" became a synonym for pterosaurs in general and for the pterodactylus and pteranodon specifically. Most lay people, along with Hollywood screenwriters, continue to use the term. "Working paleontologists never refer to 'pterodactyls,' instead focusing on individual pterosaur genera," the site states.
Pterodactylus was discovered in 1784. The pteranodon was discovered in the mid-19th century. Later paleontologists counted numerous individual species among each of these genera.