Dispersed seed-megaspores (Granditetraspora zharkovae Arkhangelskaya and Turnau) from the Givetian of Western Pomerania, Poland

The dispersed megaspore tetrads, Granditetraspora zharkovae Arkhangelskaya and Turnau, a species recorded previously from mid-Givetian deposits of European Russia, have been found in the same stratigraphical position in Western Pomerania in Poland. On the basis of well-preserved material, the diagnoses of the morphogenus Granditetraspora and the species G. zharkovae are emended. Seed-megaspores are relatively large microfossils, and thus they have low fossilisation potential outside the areas of their origin. The fact that they have been recorded from several localities separated by hundreds of kilometres suggests that plants that were the seed plant precursors must have been common component of mid-Givetian vegetation, and that the earliest stages of seed plant evolution originated earlier. The possession of reproductive structures that were relatively large and nutrient rich, and may had been dispersed when still enclosed in a sporangium, is an advantage for plants that grew in a hot, periodically arid climate of the Givetian.