Chitinozoan stratigraphy in the Ashgill and Llandovery

Synopsis: There is little published information on chitinozoan faunas from sections with continuous sedimentation across the Ordovician–Silurian boundary. Most boundary sections from which chitinozoans have been described include a hiatus. To aid determination of the extent and by hiatus, the ranges of thirty-one diagnostic chitinozoan species from Ashgill and Llandovery strata are documented, with reference to the British standard graptolite zonation. The composition of the chitinozoan faunas at the Ordovician–Silurian boundary is discussed, and the influence of ecological factors is assessed.