Morphology versus molecules in moss phylogeny: new insights (or controversies) from placental and vascular anatomy in Oedipodium griffithianum

New data on the placenta and water-conducting cells of Oedipodium griffithianum challenge current ideas on moss phylogeny. The placental region in O.?griffithianum consists of cells with highly convolute wall labyrinths on both the sporophytic and gametophytic side. This type of placenta distinguishes an assemblage of mosses including Tetraphis, Buxbaumia and all arthrodontous mosses but is not found in basal lineages including polytrichopsid mosses. Other features that distinguish Oedipodium from polytrichopsid mosses are the foot entirely ensheathed by the parenchymatous tissue of the gametophyte vaginula, the lack of a necrotic foot tip, the lack of intercellular spaces in the foot parenchyma and the presence of typical bryopsid hydroids with uniformly thin cell walls in the leafy shoot. These results do not support molecular phylogenies resolving Oedipodium as the sister group to polytrichopsid mosses or to all peristomate mosses, but are compatible with a sister relationship to a clade encompassing Tetraphis, Buxbaumia and arthrodontous mosses.