Orthopithonella collaris sp. nov., a new calcareous dinoflagellate cyst from the K/T boundary (Fish Clay, Stevns Klint/Denmark).

A new calcareous dinoflagellate cyst species, Orthopithonella collaris sp. nov., is described from the Cretaceous/Tertiary (K/T) boundary clay (Fish Clay) of Stevns Klint, Denmark, on the basis of SEM studies and light-microscopic analyses of thin sections of single specimens. The species has been found exclusively in the Fish Clay and as such may be a potential marker for the K/T boundary. Its pulse-like occurrence is thought to be due to the abrupt, relatively short-term ecological catastrophe associated with the K/T boundary event.