New Early Triassic ammonoid faunas from the Dienerian/Smithian boundary beds at the Induan/Olenekian GSSP candidate at Mud (Spiti, Northern India)

New collections at the Induan/Olenekian boundary GSSP candidate at Mud (Himachal Pradesh, Northern India) lead to the recognition of several well preserved ammonoid faunas that significantly improve the biostratigraphic resolution in the beds underlying the proposed GSSP level. In ascending order, the new biostratigraphical sequence comprises: the Ambites lilangense beds, the Fuchsites markhami beds, the Kingiteslens beds, the Prionolobusrotundatus beds, the Flemingites bhargavai beds, the Kashmiritidae gen. nov. A beds and the Vercherites cf. pulchrum beds. The faunas from Bed 10, located about 1 m below the proposed GSSP level, contain certain ammonoids with typical early Smithian affinity (Flemingitidae, Kashmiritidae) and thus reflect the beginning of the early Smithian evolutionary radiation. Seen from an evolutionary point of view, the Dienerian/Smithian boundary can therefore be placed just below Bed 10. Ideally, the stage boundary should also be intercalibrated with other biological, chemical or physical proxies as additional tools for world-wide correlations.Four new species (Flemingites bhargavai, Kingites korni, ?Kingites parkashi and Xenodiscoidesvariocostatus) and two new genera (Mudiceras, Vercherites) are described.