Middle and late Smithian (Early Triassic) ammonoids from Spiti, India

Abstract

The 'Parahedenstroemia' beds in the Mikin Formation at the Mud, Guling, Lalung and Losar localities in the Spiti area (Himachal Pradesh, northern India) yield abundant and well-preserved Smithian (Early Triassic) ammonoid faunas. Our data allow the construction of a high-resolution ammonoid succession spanning the middle to latest Smithian time interval. The new biostratigraphical succession comprises the following eight distinct ammonoid faunas (in ascending order): the Brayardites compressus beds; the Nammalites pilatoides beds, subdivided into the Escarguelites spitiensis horizon and the Truempyceras compressum horizon; the Pseudoceltites multiplicatus beds; the Nyalamites angustecostatus beds; the Wasatchites distractus beds; the Subvishnuites posterus beds; and the Glyptophiceras sinuatum beds. This faunal succession correlates with other Tethyan successions including the Salt Range (Pakistan), Tulong (South Tibet) and Guangxi Province (South China). The new genera Escarguelites, Hermannites, Kraffticeras, Nuetzelia and Steckites and six new species Escarguelites spitiensis, Hermannites rursiradiatus, Nuetzelia himalayica, Steckites brevus, Subvishnuites posterus and Truempyceras compressum are described.