The PhD student Nils Schorndorf participated in a study of an international research team led by Dr. Christina Ifrim from the Jura Museum in Eichstätt, Germany, which analyzed and compared 154 specimens of the giant ammonite genus "Parapuzosia". This giant ammonite inhabited the Atlantic Ocean of the Upper Cretaceous, some 85 to 80 million years ago. The results of the study provide insights into the ontogeny and evolution of Parapuzosia (P.) seppenradensis. The concentration of adult shells of Parapuzosia within the study sites points to a monocyclic reproduction strategy in this giant cephalopod. An increase in individual shell size is detected throughout the Santonian and into the early Campanian, where maximum shell sizes were reached on both sides of the North Atlantic. Whether the coeval increase in size of mosasaurs, the top predators in Cretaceous seas, caused ecological pressure on Parapuzosia towards larger diameters remains unclear.
Reference: Ifrim C, Stinnesbeck W, González González AH, Schorndorf N, Gale AS (2021) Ontogeny, evolution and palaeogeographic distribution of the world’s largest ammonite Parapuzosia (P.) seppenradensis (Landois, 1895). PLoS ONE 16(11): e0258510. https://doi.org/10.1371/journal.pone.0258510 (go to)