Abstract
The Famennian is a period of increased taxonomic diversity for the first representatives of the major plant groups, especially the spermatophytes (i.e. the seed plants) that, today, represent the most abundant and diversified plant group on Earth [1,2]. Early spermatophytes evolved a unique ovule-centered reproductive syndrome that allowed them to germinate and grow rapidly in disturbed habitats and, secondarily, to colonize dry habitats unfavorable to the reproduction of their free-sporing predecessors [3,4] (Fig. 1). In these ovulate organisms, the female gametophyte grows and produces gametes inside the indehiscent megasporangium (nucellus) that differentiates a pollen chamber retaining the pollen grains in its apical part. An integument encloses the nucellus. Like the Runcaria protovule that preceded them by 20 million years, Famennian ovules were all surrounded by a cupule, except perhaps Spermolithus and Warsteinia [5–7]. The latter, however, have been found isolated and may also have had a cupule remaining on the plant that produced them.