Sporoderm ultrastructure of some Devonian and Permian representatives of <i>Biharisporites</i> and their botanical affinity

The megaspore genus <i>Biharisporites</i> has a very wide stratigraphic range, being recorded from the Devonian to the Cretaceous. However, <i>in situ</i> these megaspores are known only from the Middle–Upper Devonian, from archaeopteridalean sporangia. Post-Devonian producers of <i>Biharisporites</i> are so far unknown; the parent group can only be hypothesized from the spore morphology and ultrastructure, and from the composition of contemporaneous assemblages of macroremains. To contribute to the understanding of the botanical affinity of dispersed megaspores of the genus, we undertook a comparative ultrastructural study of several <i>Biharisporites</i> species from the Middle Devonian of Russia and the Lower Permian of India. Surprisingly, we found exclusively lycopsid variants of the sporoderm ultrastructure not only in the Permian spores, but also in the Devonian. Therefore, some megaspores of <i>Biharisporites</i> were produced by lycopsids even in the Middle Devonian. Megaspores of <i>Biharisporites</i> morphology have been produced by different groups of spore-bearing plants since the Middle Devonian, and the genus <i>Biharisporites</i> is heterogeneous.