How did Mary Anning become the greatest fossil hunter ever known? What was an ichtyhosaur and why was it such an important discovery? Why did Mary become the inspiration for a famous tongue twister? The Natural History Museum has called Mary Anning the greatest fossil hunter ever known. Anning discovered fossils that shook up the way we look at the natural world and how it has changed over time. Her achievements inspired many scientists and paved the way for the development of geology as a science.