Buried deep beyond the veil of extinction: Euphyllophyte relationships at the base of the spermatophyte clade

Abstract

Our results support the groups defined by traditional taxonomy, resolve Stenokoleales nested among the lignophytes, and indicate that seed plants may share a closer ancestor with Stenokoleales than with aneurophytes. Additionally, our trees suggest a Givetian minimum age for the seed plant ancestor, a late Emsian minimum age for the Stenokoleales, and early Emsian minimum ages for lignophytes, the bilateral clade, and the aneurophyte ancestor.

Morphological (and not anatomical or reproductive) features define early vascular plant phylogenetic relationships

“…This taxon had many missing characters states (e.g., its anatomy is currently unknown). The 54‐character matrix failed to group Aneurophyton with a Rellimia ‐ Tetraxylopteris dyad (see Toledo et al., for similar findings). In addition, the seed plants Elkinsia and Lyginopteris appear on separate branches within the trimerophyte‐euphyllophyte clade.…”

“…The Silurian–Devonian time period cast a long shadow over subsequent vascular plant evolution (DiMichele et al., ; Stein et al., ; Toledo et al., ). Many of the anatomical, morphological, and reproductive features characterizing the sporophytes of modern‐day plant lineages, such as the distinctive leaf morphology and stem anatomy of contemporary lycophytes as well as ferns, Equisetum , and other euphyllophytes, evolved during this period of plant evolution (summarized by Taylor et al., ).…”

Multiple origins of dichotomous and lateral branching during root evolution

“…We next investigated root branching in members of the lignophytes 9,21 , the group containing all extant seed plants. It is hypothesized that seed plants evolved from a progymnosperm ancestor.…”

Tree of death: The role of fossils in resolving the overall pattern of plant phylogeny

“…However, when successively deeper phylogenetic nodes are addressed, the clades are increasingly likely to have suffered large percentages of extinction. Where 90% or more of species richness has been pruned and is absent from the living flora, very deep nodes of the tree may not be represented by any living species at all (e.g., Toledo et al., ). As a result, the inclusion of extinct species has much greater potential to alter the topology of the resulting trees when deeper internal nodes are addressed.…”

“…Toledo et al. () explore relationships at the base of the lignophyte clade, as revealed by the most ancient stem‐group seed plants and several other related groups, none of which is represented in the modern flora, but all of which are vital for our understanding of the evolution and homologies of leaves, stelar architecture, branching, gymnospermous reproduction, and seeds.…”