A reassessment of Permian parareptiles using 3D imaging technologies, and their importance for early amniote evolution and ecology

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The Permian period was a time in Earth’s history in which modern terrestrial ecosystems were taking form, a major component of these ecosystems were amniotes (fully terrestrial tetrapods). Amniotes are traditionally divided into the sister-clades Synapsida (the evolutionary lineage of modern mammals) and Sauropsida (the evolutionary lineage of modern reptiles and birds). One of the early amniote groups that was diversifying during the Permian was Parareptilia, with this clade gaining a cosmopolitan distribution by the end of the Permian and surviving the greatest mass extinction in Earth’s history at the Permian-Triassic boundary. However, there is still much that is not known regarding parareptilian evolution and ecology, especially prior to the late Permian. The Russian parareptiles represent an extensive and understudied component of Permian localities, as there are major gaps in our knowledge of their anatomy, phylogenetic interrelationships, palaeoecology, and biogeography. Moreover, the intra- and interrelationships of parareptiles and early amniotes as a whole, are far from resolved and several traditional hypotheses have recently been challenged. To resolve some of these issues, we propose an in-depth collaborative German-Russian research project to re-evaluate selected members of the unique Russian parareptile fauna (including the clades Nycteroleteridae, Bolosauridae, Nyctiphruretidae, Lanthanosuchoidea) using modern approaches. In order to accomplish this our proposed research will utilize state-of-the-art 3D-imaging technologies, specifically synchrotron and micro-CT scanning and 3D segmentation of Russian parareptile taxa, especially their skulls, in order to elucidate new details regarding their anatomy. The information obtained from this new data will be used for revised and updated descriptions, expanded and revised phylogenetic analyses, quantitative analyses, and macroevolutionary interpretations. Overall, this research aims to provide a better understanding of Russian parareptiles and to facilitate the integration of these taxa into the bigger picture of amniote evolution during the late Palaeozoic. Re-evaluating these Russian parareptile clades will also be instrumental for testing the monophyly of Parareptilia, which has never been adequately assessed since the inception of the clade.