Ammonites were marine animals belonging to the phylum Mollusca and the class Bivalvia. They had a coiled external shell similar to that of the modern nautilus.
Ammonites lived during the Jurassic and Cretaceous periods. The Jurassic Period began about 201 million years ago and the Cretaceous Period ended about 66 million years ago. The ammonites became extinct at the end of the Cretaceous, at roughly the same time as the dinosaurs disappeared.
The use of ammonites in stratigraphy was pioneered in the 1850s by two Germans - Friedrich Quenstedt of Tübingen (1809-1889) and his one-time pupil, Albert Oppel of Munich (1831-1865). Their work was based on the ammonites of the Swabian and Franconian Alb of southern Germany - the eastern extension of the Jura Mountains of France and Switzerland, from which the Jurassic Period takes its name. |
