Constraining assembly time of some blocks on eastern margin of Pangea using Permo-Triassic non-marine tetrapod records

The supercontinent Pangea was mainly formed during the Permian, but when it reached maximum land is unsure because the configuration of the East Asian blocks during the Permo-Triassic is still highly debated. Fossil tetrapods provide one of the best calibrations to the time of connection between continents, but the data of Permo-Triassic tetrapods have rarely been applied in the previous reconstructions. Here we review the oldest records of non-marine tetrapods on the East Asia blocks and use them to discuss the timing of connection between continents during the Permian and Triassic. The distribution of Seymouriamorpha shows the Kazakhstanian was connected to the Baltica by land from the Cisuralian. The diverse Dashankou Fauna indicates that the Alxa Block amalgamated to Pangea at least in the Guadalupian (older than 266 Ma). The questionable footprints and late Permian dicynodont assemblage from the North China show the North China Craton may have been connected to the main part of Pangea from the Guadalupian, and became part of Pangea at least by 256 Ma. The late Permian Laotian tetrapods support the hypothesis that the South China Block already collided with the North China and the Indochina blocks by the end of the Permian, and there was a land route for the migration of non-marine tetrapods.