Palaeoecological and Palaeogeographical Reconstructions of Formation Conditions for Late Cretaceous Sediments of the Ulyanovsk–Saratov Foredeep, which Contain Burrows of Polychaete Worms

The localities of worm burrows, Lepidenteron lewesiensis polychaete, in the Upper Cretaceous sediments of the Lower Volga region are described for the first time, including a comprehensive lithological and paleontological description of the Upper Cretaceous formations of the Ulyanovsk–Saratov foredeep. Paleoecological models of paleocenosis habitats are proposed and paleogeographic conditions for the formation of sediments containing polychaete burrows are clarified.