Palynologically calibrated vertebrate record from North Dakota consistent with abrupt dinosaur extinction at the Cretaceous-Tertiary boundary

New data from 17 Cretaceous-Tertiary (K-T) boundary sections and 53 vertebr ate sites in the Hell Creek and Fort Union Formations in southwestern North Dakota document a 1.76 m barren interval between the highest Cretaceous ve rtebrate fossils and the palynologically recognized K-T boundary. The bound ary is above the formational contact at 15 localities and coincident with i t at two, demonstrating that the formational contact is diachronous. Dinosa urs are common in the highest Cretaceous vertebrate samples and a partial d inosaur skeleton in the Port Union Formation is the highest recorded Cretac eous vertebrate fossil in this area.