Mariopteris Fern Fossil 1.jpg
Mariopteris Fern Fossil
Eastern Kentucky, USA
Pennsylvanian Period (~330 Million Years Ago)
The Medullosales is an order of pteridospermous seed plants characterised by large ovules with circular cross-section, with a vascularised nucellus, complex pollen-organs, stems and rachides with a dissected stele, and frond-like leaves. Their nearest still-living relatives are the cycads. Most medullosaleans were small to medium-sized trees. The largest were probably the trees with Alethopteris fronds - these fronds could be at least 7 metres long and the trees were perhaps up to 10 metres tall. Especially in Moscovian times, many medullosaleans were rather smaller trees with fronds only about 2 metres long, and apparently growing in dense, mutually supporting stands. During Kasimovian and Gzhelian times there were also non-arboreal forms with smaller fronds (e.g. Odontopteris) that were probably scrambling or possibly climbing plants.
unranked clade: †Radiatopses