Lyginopteridales

[3] During early and most of middle Pennsylvanian times the Medullosales took over as the more important of the larger pteridosperms but the Lyginopteridales continued to flourish as climbing (lianescent) and scrambling plants.However, later in Middle Pennsylvanian times the Lyginopteridales went into serious decline, probably being out-competed by the Callistophytales that occupied similar ecological niches but had more sophisticated reproductive strategies.[8] It is widely thought that this arrangement was derived from an ancestral condition where there was a cluster of sporangium-bearing axes, but where only one eventually retained its megasporangium, the others forming the surrounding pre-integument.The stratigraphically older lyginopteridaleans had trusses of synangia borne on slender axes, which were attached to vegetative fronds;[22] these are referred to the fossil genera Telangium if they are anatomically preserved or Telangiopsis if they occur as adpressions.[23] The Mississippian-aged lyginopteridaleans tended to have a simple protostele usually surrounded by secondary wood, but in later forms there was a eustele with a central core of pith or mixed-pith.Some authors[25][26] also recognise the Mariopteridaceae for the distinctive group of Pennsylvanian-aged lianescent plants with Mariopteris fronds, although details of their reproductive structures are unknown.