There are a number of enigmatic gymnospermous plants that deserve mention because of their interesting morphology and, in some instances, unusual internal structure. Some of these are known from very few specimens or are restricted both geographically and stratigraphically, for example, the Hermanophytales. In other instances, the plants are known in some detail, but their affinities continue to ... [Show full abstract] remain elusive, for example, the Vojnovskyales. Some, such as the gnetophytes, have been included in phylogenetic analyses of seed plants. As additional specimens of existing taxa are discovered, which are more completely preserved, together with the discovery of new genera and species, some of the enigmatic taxa today will perhaps be easier to classify in the future.