This image is of the worlds largest ammonite (replica. *sigh*) from the Natural History Museum of Los Angeles when I visited in December 2014.
The species is Parapuzosia seppenradensis and was found in a stone quarry near Seppenrade, Germany. The original is suggested to be 78 million years old. It has a diameter of 180cm (although I have found sizes ranging from 170cm to 259cm on the internet) and a weight of 3.5 tonnes.
The fossil was discovered by Theodore Nopco (a local historian and zoologist) in 1895. The original is now on display at the Munster Natural History Museum (Westfalischen Landesmusem fur Naturkunde).