Because they are morphologically simple, psilotophyta (whisk ferns) have traditionally been thought to be a basal group in the radiation of land plants. molecular phylogenies have challenged this hypothesis and support the alternative hypothesis that

Molecular phylogenies have challenged this hypothesis and support the alternative hypothesis that they might be phylogenetic, coming from an intricate linage structure.

Explanation:

Psilotophyta were traditionally graded as monophyletic, vascular plants that resemble their immediate ancestor with gradual increases in complexity. However, Molecular phylogenies has challenged this classification by studying these vascular plants’ genetics and hereditary material. By analysing nucleotide and amino acid sequences, Molecular phylogenies have challenged the current topologies of whisk ferns as they might have evolved from more than one ancestor. Instead of descending from a single lineage, these fern-like vascular plants may be part of a taxon with not common ancestor.  

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