Why is the fossil record of gnetophytes difficult to interpret?

The fossil record of the division Gnetophyta is considered obscure, and its evolutionary origins remain unclear.1

The difficulty in interpreting this record stems from several factors:

• Reliance on Pollen: The existence of gnetophytes in the fossil record is primarily based on the presence of pollen grains that resemble those of the modern genera Ephedra and Welwitschia. These pollen types have been identified in deposits dating as far back as the Permian Period.21
• Scarcity of Macrofossils: While pollen is relatively abundant, physical remains of gnetophytan plants are rare. Potential specimens found in Upper Cretaceous deposits are unlike any extant species, making it challenging to establish clear links to modern groups.1
• Morphological Ambiguity: Although some fossils exhibit features such as leaf venation similar to Welwitschia or are associated with specific pollen types, the overall lack of well-preserved, identifiable plant structures complicates efforts to trace their lineage or confirm their relationship to other gymnosperms and angiosperms.21