Jost WIEDMANN'S share in recognition of the latest Maastrichtian Pachydiscus from the Nasiłów section (Middle Vistula Valley, Central Poland)

Abstract

The occurrence is reported of the two pachydiscid species, Pachydiscus (Pachydiscus) gollevillensis (D'ORBIGNY, 1850) and Anapachydiscus cf. terminus WARD & KENNEDY, 1993, from the topmost Maastrichtian siliceous chalk exposed at Nasiłów in the Middle Vistula Valley, Central Poland. The collected specimens come from a level situated about 1m below the Nasiłów hardground, and 1.3m below the residual lag marking the K/T boundary. These findings are discussed in terms of their bearing on a biostratigraphic subdivision of the Upper Maastrichtian, and an ammonoid extinction at the K/T boundary.