Although different analyses have produced somewhat different topologies, most preserve this clade and recognize the gnetophytes as sister to the flowering plants. Syndetocheilic stomata in the anthophytes. Pentoxylon, like Glossopteris and Dicroidium foliages, is a Gondwanan taxon, which has been found in India, Australia and New Zealand. Pentoxylon first appears in the later part of the Paleozoic, but its greatest diversity and abundance appears to be in the Jurassic, continuing into the Early Cretaceous. Note that this eustele arrangement is more like that of Medullosa than that of either conifers or angiosperms.
Foliage arises from short shoots, where leaf scars are commonly visible.
Leaves a long and narrow with a prominent mid-rib and secondary veins arising at right angles to it and continuing, unbranched to the leaf margin. In syndetocheilic stomata, the guard cell mother cell gives rise to a pair of guard cells and one or more pairs of subsidiary cells. Individual cupules contain and almost completely enclose a single ovule. The ovule integument is composed of an inner sclerenchymized layer and a fleshy outer layer. Pollen organs are also born in clusters on short shoots.