The Yarenskian Gorizont ("Yarenskian Horizon") is a major biostratigraphic unit in Russia corresponding to Upper Olenekian-age terrestrial sediments. It lies above the Ustmylian Gorizont of the , and is located below a short unconformity overlain by the Donguz Gorizont. Some paleontologists elevate the Yarenskian to a supergorizont and subdivide it into two smaller units: the older Fedorovskian Gorizont and the younger Gamskian Gorizont. Others prefer to consider the Fedorovskian and Gamskian to be subgorizonts or members of the Yarenskian. Vertebrate index fossils of the Fedorovskian include the lungfish Gnathorhiza, the trematosaurid Inflectosaurus, and the procolophonid . In the Gamskian, these index fossils are replaced by Ceratodus, Trematosaurus, and Kapes, respectively. The Yarenski