Аннотация
The article presents the first data of the U-Pb LA-ICPMS dating of the tetrapod fauna “Mastodonsaurus” (Middle Triassic). The U-Pb age (241.6 ± 1.0 Ma) of the sediments directly underlying the layers of the Inder Formation with the fauna “Mastodonsaurus” in the Kok-Tau section (Pre-Caspian Depression) indicates that the base of the Inderian Regional stage roughly corresponds to the Anisian-Ladinian boundary and can be used as the lower age limit for the distribution of this fauna. The obtained radioisotopic dating, as well as palaeontological data on the bone-bearing Bukobayian Regional stage of the Southern Urals, place the stratigraphic range of the fauna “Mastodonsaurus” within the Ladinian Stage. A palaeogeographic model of the sediment accumulation in the Eltonian and Inderian time is proposed.