Pollination, the successful transfer of pollen from the pollen sacs (microsporangia) into proximity with the ovule, is the essential precursor to fertilisation and therefore to sexual reproduction in seed plants. Pollination has been studied most intensively in angiosperms, although few species have been examined in detail compared with the great variety of flowers within the group (e.g. Proctor et al., 1996; Thien et al., 2009). Pollination in extant non-angiosperm seed plants has received less attention, but studies over the past few decades now provide a more complete context within which pollination in angiosperms can be evaluated and studied (e.g. Owens et al., 1998).
Interpretation of pollination in extinct plants faces significant difficulties. Only rarely is there relatively direct evidence of flower–pollinator interactions (e.g. insect gut contents, coprolites, insects preserved within flowers, insects carrying pollen) and interpretations of pollination in extinct plants therefore depend heavily on extrapolations to extant taxa based on structural similarities. This often leads to plausible interpretations, but it may also be constraining. There is no a priori reason why the spectrum of plant–pollinator interactions existing today should also include all of those that existed in the past, and inferring floral function from floral structure, even in extant plants, can sometimes be difficult. It is therefore especially challenging to infer pollination in extinct seed plants (e.g. Caytonia, Bennettitales) that have no clear close living relatives.