Near the beginning of the film, in the lobby of the Natural History Museum, the tail of the Diplodocus skeleton is raised up off the ground. The film is set in 1911, but that skeleton had a dragging tail until it was remounted in 1993.
The Diplodocus skeleton was not located in the main hall of the Natural History Museum in 1911, as shown in the film. It had been in the Reptile Hall (now Human Biology) to the west of the main hall since its installation in 1905. It was only moved to the main hall in 1979.
When the Allosaurs attack the Indian camp Challenger sees one and tries to shoot it with his sawed off shotgun. He fires two shots and a split second later a third. There was not enough time for him to reload.
The lost world is located on the top of a large plateau, yet scenes, especially around Lake Gladys, show mountain ranges rising from the area. A plateau cannot have mountains that start at the top of the plateau.
The Plateau in the film has been described as a world that is "cut off from evolutionary development." If that were true then dinosaurs from different eras would not be in the same place, nor would there be any ape-men or humanoids.