Some of the neck bones in the specimen were displaced and it is possible that this led Cuvier to suggest that the specimen may have been a fraud made up from the bones of several different animals. A meeting of The Geological Society was called in 1924 and this concluded that the plesiosaur specimens were genuine. Cuvier later admitted that he had been mistaken.
It is believed that Mary Anning never “improved” her specimens but the same is not true for other collectors of that era. However, that is another story.
You can read more about Mary Anning, William Coneybeare and other scientists here.