Lower and Middle Triassic footprints-based biochrnology in the Italian Southern Alps

The Early and Middle Triassic ichnoassociations of the Italian Southern Alps appear particularly important due to their excellent state of preservation and the ample vertical distribution of the dated trampled levels. On the basis of the ranges of single ichnotaxa, it is possible to define a series of different associations, characterized by different evolutionary stages. They correspond to informal evolutionary units that can be estabilished as faunal units (FUs). The Scythian is characterized by the presence of Rhynchosauroides schochardti that disappears in the Anisian. In the Anisian, characterized by the appearance of Rhynchosauroides tirolicus) a progressive increase in the complexity of the ichnoassociations from the Bithynian to the Illyrian is documented. In the Bithynian - Early Pelsonian interval the faunal assemblage is dominated by Parasynaptichnium gracilis and Synaptichnium pseudosuchoides. The Early Pelsonian - Early Illyrian interval is characterized by the dominance of Isochirotherium delicatum and Brachychirotherium circaparvum.