The Medullosales is an extinct order of
pteridospermous seed plants characterised by large
ovules with circular cross-section and a vascularised
nucellus
In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the ''integument'', forming its outer layer, the '' nucellus'' (or remnant of the megasporangium), and the ...
, complex pollen-organs, stems and
rachides with a dissected
stele
A stele ( ),Anglicized plural steles ( ); Greek plural stelai ( ), from Greek language, Greek , ''stēlē''. The Greek plural is written , ''stēlai'', but this is only rarely encountered in English. or occasionally stela (plural ''stelas'' or ...
, and
frond
A frond is a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group. Other botanists allow the term frond to also apply to the lar ...
-like leaves.
Their nearest still-living relatives are the
cycads
Cycads are seed plants that typically have a stout and woody ( ligneous) trunk with a crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants of a species are either male or ...
.
Most medullosales were small to medium-sized trees. The largest specimens were probably of genus ''
Alethopteris'', whose fronds could be 7 metres long
and the trees were perhaps up to 10 metres tall. Especially in
Moscovian
Moscovian may refer to:
*An inhabitant of Moscow, the capital of Russia
*Something of, from, or related to Moscow
* Moscovian (Carboniferous), a stage of the Carboniferous in the ICS geologic timescale