Harry Hoyt's 1925 silent film, The Lost World, was one of the first sci fi adventure type films made that featured dinosaurs.
Much of its plot was re-worked in King Kong, made a decade later. Taken from the story by Arthur Conan Doyle, creator of Sherlock Holmes, the tale is much the same.
A captured dinosaur- a Brontosaurus, is brought back to a big city (this time London) and havoc ensues. The beast escapes, and the man who captured it loses all- a future, money, and his love.
King Kong was not the only film to borrow this plot, but few films can be claimed to have started a genre in film.
The Lost World, while an important film, in the sense just mentioned, is not a great film, even by the more lax standards of the silent film form. But, it is a fun film, and because it is in the public domain, you can watch it all here, at Cinemension.