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.
Thus, scrambling growth cannot be determined directly from the impression/compression fossil record of
pteridosperms. However, certain features of
pteridosperm frond architecture (e.g., large fronds with lax appearance, thin, flexuous stipes and rachides, wide-angled pinnae [Fig.
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.
Late Gzhelian
pteridosperms with callipterid foliage of the Donets Basin, Ukraine.
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. Rev.
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. The best approximation in answer to their question is as yet supplied by the three cauline specimens described.