Significance of monosulcate pollen abundance in Mesozoic sediments

Monosulcate pollen was produced by at least six plant orders in the Mesozoic. Megafossils of these orders are abundant in many Mesozoic sediments, but dispersed monosulcate pollen grains are commonly less than 10% of total sporomorphs (spores and pollen) in a sample. This paper presents possible explanations for the different relative frequencies of megafossils and pollen grains of monosulcate-producing plants (some of the explanations apply to only a few taxa): fragility of the pollen exines, destruction of the pollen on the plant by insects, poor pollen dispersal because of zoophily and small plant size, and, probably most importantly, overrepresentation of the plants by their generally deciduous leaves. Mesozoic monosulcate pollen was different in several ways from pollen of modern gymnosperms; furthermore, monosulcate-producing plants were not as abundant in the Mesozoic vegetation as has been generally thought.