The lower Gondwana gymnosperms and their relationships

Abstract

Gymnospermous remains in Lower Gondwanas consist of petrified woods, leaves and fructifications. While some woods may belong to Glossopteridales, the affinities of others are uncertain. Most of the Lower Gondwana leaves, unlike their contemporaneous northern counterparts, are simple. Among them one can recognize at least three definite alliances, viz. Glossopteridales, Noeggerathiopsidales and Coniferopsida. The unique leaf attached fructifications of the Glossopteridales may suggest some affinity with the pteridosperms. The leaves of Noeggerathiopsis (Noeggerathiopsidales) are Cordaites-like but no typical associated cordaitean stems and fructifications have been found. Among the Coniferopsida the lack of a female cone in Buriadia may suggest a very primitive conifer. Some other forms like Walkomiella, Searsolia and Paranocladus also appear to be coniferopsid. There are also some Incertae like Caulophyllites, Cheirophyllum, Dunedoonia and Psygmophyllum whose precise affinities are unknown. Detached sporangia and seeds occurring in the Lower Gondwanas not only confirm the existence of the three groups of gymnosperms suggested by other megafossils but they also indicate that they may have been more diverse.