Tabulate corals from the Takche Formation (Ordovician-Silurian), Spiti, Tethyan Himalaya, and their biostratigraphical and palaeobiogeographical significance

We report tabulate corals Leleshusia and Palaeofavosites from the lower and upper parts of Unit P13 of the Pin Member, Takche Formation, Pin Valley (Spiti, Tethyan Himalaya), India. The unit corresponds to the Katian Amorphognathus ordovicicus Biozone. The presence of Leleshusia in the lower part of this unit supports a late Katian age, consistent with its stratigraphic restriction to the Katian. In contrast, the occurrence of Palaeofavosites hystrix, a characteristic element of the Edgewood fauna (Hirnantian–Rhuddanian), in the upper part of this unit indicates a probable Hirnantian age, suggesting that Unit P13 spans the Katian–Hirnantian (late Ordovician) transition. These corals are recorded from strata below the Ordovician-Silurian boundary in Spiti. The stratigraphic correlation with the Katian-Hirnantian (KaH) excursion validates this age assignment. The occurrence of Leleshusia and Palaeofavosites in the Himalaya expands their paleobiogeographic range along the northern Gondwanan margin and indicates faunal exchange between the Indian Plate and other contemporaneous paleocontinents during the late Great Ordovician Biodiversification Event (GOBE).