Resolving the phylogeny and biogeographic history of early Crocodylia through total evidence analysis and exceptionally preserved Eocene fossils from Vietnam

• Applicant: Dr. Márton Rabi, Ph.D.
• Subject Area: Palaeontology
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 417629144

Representatives of Crocodylia, the group including modern-day alligators, caimans, crocodiles, and gharials, formed a major element of lowland ecosystems during the Paleogene and have an extensive fossil record accordingly. This makes them an excellent model clade for addressing a broad range of questions in macroevolution such as the environmental drivers of biodiversity in deep time. Of particular interest, is their biogeographic history as intercontinental dispersals played a major role in their diversification facilitated by the warm high-latitude climate of the Eocene. The Paleogene biogeographic history of crocodylians remains largely uncertain because phylogenies including fossils are instable due to limited sampling. The most critical issues include the markedly poor Paleogene fossil record of Asia, a continent that evidently had a major role in the evolution of Crocodylia based on present-day diversity alone. Another major factor is the limited utilization of molecular data in phylogenetic inference in combination with morphology from extant and extinct species. We here propose to extensively expand sampling by the addition of fossil data from undescribed Eocene crocodylians collected by the University of Tübingen during a DFG BO 1550/11-1, 2 - funded project in Vietnam. The abundance, exceptional preservation, and diversity (representing each of the three major extant lineages with several ontogenetic stages) makes this new fossil assemblage by far the most important among crocodylian faunas from the Paleogene of Asia. The new material ranks among the best-preserved fossils from North America and Europe thereby, for the first time, allowing meaningful comparisons of faunas across Laurasia. Novel osteological data from the Vietnamese taxa as well as key species from Europe and North America will be combined with molecular data in order to elucidate the early diversification and Laurasian biogeographic history of Crocodylia. The expected results will have important implications for intercontinental paleogeographic reconstruction and faunal interchange during the early Paleogene.

• DFG Programme: Research Grants
• Co-Investigator: Professorin Dr. Madelaine Böhme