New plants of Gnetales from Early Cretaceous of China, and its bearing on the early evolution of Ephedraceae and Welwitschiaceae in Gnetales

Abstract

The Gnetales are a higher group of Gymnosperms, but our current knowledge of the morphology of the early Gnetales is lacking. Most known specimens are fragmentary, which makes it difficult to elucidate the geological history and the early diversity and evolution of the group. New well-preserved specimens have been discovered in Liaoning, north China, and a detailed morphological study was carried out. The material belongs to three new genera: Spinobractea lanceoleta gen. et sp. nov., Latibractea divisa gen. et sp. nov. and Constrobilus ovata gen. et sp. nov. The record of the Ephedraceae can be traced back to the Jurassic. The Ephedraceae were quite successful in the Cretaceous, and the plant types and the environment that they inhabited shown that the Cretaceous plants were much more varied than their living relatives. However, some types became extinct, and some features were lost. The record of the Welwitschiaceae can be traced back to the Triassic. Features of the leaf venation and the seeds are the primary features used for recognition of this family in both living and fossil plants. These features are so conservative that they have shown almost no major changes since the Triassic.