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As with all the other plant beds in this succession, medullosan pteridosperm remains are dominant and comprise Macroneuropteris scheuchzeri with cyclopterid pinnules, Neuropteris ovata, and trunks with downward-recurved petioles.
The presence of a fossil flora consisting of sphenopsids, lycopsids, cordaitaleans, a varied suite of ferns (including tree fragments), and more occasional pteridosperms, is indicative of a humid environment.
From this Psilophyton-like type were derived two lines of evolution--the lycopods, on the one hand, which retained their phylloids and dichotomous cauloids, and, on the other, all other vascular cryptogams, the pteridosperms, all gymnosperms and angiosperms.
However, certain features of pteridosperm frond architecture (e.
The structure of the Carboniferous pteridosperm frond Neuropteris ovata Hoffmann.
Literature on medullosalean pteridosperms, in contrast with other studied groups of Carboniferous plants, is very large and reflects a most intensively investigated Palaeozoic plant group.
Drifted lycopsid plants predominate in the basal limestones, whereas overlying siltstones and sandstones contain a mixed suite of drifted gymnosperms (cordaitaleans), sphenopsids (primarily calamiteans), pteridosperms and putative progymnosperms (Falcon-Lang 2003a).
and shade leaves in two Jurassic species of pteridosperms.
DiMichele and Phillips (1977) described the monocyclic Psaronius simplicicaulis from an Early Pennsylvanian bedrock valley-fill succession in Illinois (Leary 1981), where it was associated with an upland/dryland assemblage of cordaitaleans, pteridosperms, and noeggerathialians (Leary 1975, 1993).
some Paleozoic pteridosperms and is established as a character in
1990) raised the important question about cauline-borne ovules for pteridosperms.
Seasonal dryland environments were apparently colonised by ecologically stressed, fire-prone vegetation dominated by cordaitaleans and medullosan pteridosperms (Falcon-Lang 2003a, 2003b), and additionally supported a low-diversity fauna of invertebrates and tetrapods (Hebert and Calder 2004; Falcon-Lang et al.
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