Rybinskian Gorizont

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Rybinskian Gorizont, or Rybinskian Horizon, is a Lower Triassic biostratigraphic unit in western Russia. It is part of the Vetlugian Supergorizont and marks the early Olenekian, lying above the late Induan Zaplavnian Horizon and below the Sludkian Gorizont. It is sometimes called the Benthosuchus fauna because Benthosuchus, a temnospondyl amphibian, is abundant there. Other amphibians, such as Thoosuchus, also become more common, and the interval contains the oldest fossils of procolophonines and possibly early archosaurs in the region. The Rybinskian rocks are exposed in several svitas (formations) over a wide area, with the type assemblage in the Rybinskaya Svita of the Moscow Syncline and another well-known exposure in the Staritskya Svita of the Southern Urals.