It is a part of the Vetlugian Supergorizont and corresponds to the earliest part of the Olenekian stage, lying above the late Induan-age Zaplavnian Horizon[1] and below the Sludkian Gorizont.
The Rybinskian Gorizont is sometimes known as the Benthosuchus fauna, due to abundant fossils of Benthosuchus, a temnospondyl amphibian index fossil.
Related amphibians such as Thoosuchus also increase in abundance, and the interval additionally hosts the oldest fossils of procolophonines and putative true archosaurs in the region.
[2][3] The Rybinskian is exposed in several svitas (equivalent to geological formations) spread out over a wide area: the type assemblage is the Rybinskaya Svita in the Moscow Syncline, and another is the Staritskya Svita in the Southern Urals area.
This article about a specific stratigraphic formation in Europe is a stub.