The Medullosales is an extinct order of pteridospermous seed plants characterised by large ovules with circular cross-section and a vascularised nucellus, complex pollen-organs, stems and rachides with a dissected stele, and frond-like leaves.

Especially in Moscovian times, many medullosales were rather smaller, with fronds only about 2 metres long, and apparently growing in dense, mutually supporting stands.

A number of cases are now coming to light that suggest that the seeds were borne in clusters on relatively slender, branching axes,[7][8] and that these trusses of ovules would have been produced from the top of the trunk among the crown of fronds.

The pollen producing organs consisted of clusters of elongate sacs formed into a variety of cup-, bell- and cigar-shaped configurations, assigned to various fossil genera including Dolerotheca, Whittleseya, Aulacotheca and Potoniea.

When viewed in transverse section they appear to have several vascular segments passing along the length of the stem, superficially resembling the polysteles seen in tree ferns.

However, detailed study of these vascular strands has shown that they merge and split along the length of the stem and in fact represents a single dissected stele.

[5] Another distinctive type of stem in which the vascular segments are of two different sizes in transverse section (fossil genus Sutcliffia) has been linked with the parispermacean fronds.

Each branch produced by the fork has an essentially pinnate appearance, superficially resembling the fronds of many ferns, but it is now thought that they in fact consist of a series of more or less overtopped dichotomies.

[24][25] Codonospermum, Colpospermum, Polylophospermum, and Stephanospermum are so anatomically distinctive that some authors classify them each within a monotypic family (Codonospermaceae, Colpospermaceae,[23] Polylophospermaceae, and Stephanospermaceae, respectively).