Where the giants lived: the worlds largest ammonite Parapuzosia and its palaeoenvironment

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The worlds largest and likely most famous ammonite is Parapuzosia seppenradensis from the Campanian (Upper Cretaceous) of the Münsterland region in Germany. This giant was approx. 2.30 metres in diameter and was discovered 120 years ago. Little is known on the specimen and the species, as giant Parapuzosia were considered to be extremely rare. During cooperation activities and fieldwork in north-eastern Mexican state of Coahuila, however, we discovered numerous specimens in official and private collections and also found the localities, from there these giants originate. Parapuzosia appears to be a common taxon there. Here we plan to investigate these localities in order to determine the precise stratigraphic range and the palaeoenvironmental conditions during deposition. A fine-scaled biostratigraphic framework will be established providing a layer-by-layer analysis of ammonites, inoceramids, planktic foraminifers and nannofossils, and we will further calibrate this zonation by isotope stratigraphy. A morphometric and a taphonomical investigation of collected and still embedded specimens will give insight into palaeobiological aspects of giant Parapuzosia. Juvenile and adult specimens can be compared for the first time with material from both Europe and North America. The faunal elements associated with Parapuzosia (e.g. other ammonites, inoceramids) in the Mexican sections will allow us to draw further conclusions on the faunal relations between both continents. Some of these taxa also show gigantism. We will therefore discuss the question, which environmental conditions allowed for the enormous size increase in various marine molluscs in the Santonian-Campanian transition. In addition, our data will be of interest for museums worldwide that display copies of this famous German fossil. In addition, the section may be one of the completest across the Santonian-Campanian boundary at all.