Durotrigia daveyi gen. et sp. nov., an Early Bajocian dinocyst with a variable precingular archaeopyle

Abstract. Durotrigia daveyi gen. et sp. nov. is described from the Inferior Oolite (Early Bajocian) of Dorset, England. It is the earliest distinctly tabulated gonyaulacacean dinocyst with a precingular archaeopyle. The archaeopyle is apparently variable, involving the loss of between 1 and 5 precingular plates. This variability poses some interesting taxonomic problems, particularly the implications to the value of the archaeopyle type as a high-level classification criterion. Some possible causes of archaeopyle variability are discussed.