New insights into the evolutionary history of European snapping turtles (Chelydropsis) through the use of micro CT imaging

• Applicant: Dr. Tobias Massonne
• Subject Area: Palaeontology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 559793482

Snapping turtles of the family Pan-Chelydridae are an important subject for conservation, ecological and morphological studies. Today restricted to the Americas, this group was also widespread throughout Europe and Asia from the middle Eocene to the Pliocene. Although remains from at least 112 localities are known, fundamental questions remain unanswered. The actual number of species present in Europe is still under dispute, as is their phylogenetic position and the phylogeny of Pan-Chelydridae as a whole, which ultimately affects our knowledge of the dispersal of the group during the Palaeogene. In addition, we know very little about the intraspecific variation of the group, because most species are only known from very few individuals. The goals of the proposed project are therefore the following: Clarifying the number of species of Chelydropsis present in Europe by comparing well-preserved (described and undescribed) skulls and shells from several localities (Rott, Saint Henri, Saint André, Oehningen, Unterwohlbach, Steinheim, Höwenegg, Hammerschmiede), using modern myCT and digital surface scans to study the inner cranial and inner shell morphology, as well as the intraspecific variation of the genus. Further resolving the phylogeny of Pan-Chelydridae, particularly the European clade Chelydropsis, by incorporating the results obtained from the first part of the project to solve the polytomy within Pan-Chelydridae and the inconsistency currently recovered for Chelydropsis to learn more about the palaeobiogeography of the group. To achieve these goals, three publications are planned: 1) Description of unpublished material of Chelydropsis decheni from the Oligocene of southern France, housed in Basel. The material includes complete and partial carapaces of several individuals and provides a good opportunity for a needed revision of C. decheni and to determine intraspecific variations. 2) Description of excellently preserved, undescribed material from the Miocene Hammerschmiede locality. The skulls and carapaces will be analyzed using myCT and will provide new insights into the morphology of Chelydropsis murchisoni, which will later be important for testing the validity of several species that have been synonymized with C. murchisoni based on external morphological characters alone. With more than 150 specimens, the Hammerschmiede offers the unique opportunity to study for the first time intraspecific variation on a larger scale, not only in C. murchisoni, but in Chelydropsis as a whole. 3) Incorporating the results of the other two projects and focusing on the phylogeny of Chelydropsis and subsequently on the palaeobiogeography of Chelydropsis and the entire family Pan-Chelydridae. The aim is to create a new standard taxon-character matrix for pan-chelydrids, which will be expanded in the future to finally resolve the current polytomies and inconsistencies in the phylogeny.

• DFG Programme: WBP Fellowship
• International Connection: Switzerland
• Host: Professor Dr. Walter Joyce