The occurrence Glossopteris leaves and certain vertebrates throughout the Gondwana countries were important early evidence for the theory of continental drift at the beginning of the century, long before it was a generally accepted concept and long before the mechanism of plate tectonics was known. Glossopteris plants had a wide variety of unusual reproductive structures that appear to be attached to the central midrib of a leaf. They are either ovulate or pollen structures. Because most are found as compressions or impressions and there are not any good modern analogues they have been difficult to interpret. The stems were woody and bore leaves in a tight helix that appear to be whorled and the roots have large air channels and look like vertebrae in cross section.
Pollen is bisaccate and striate.
Petrified Glossopteris fossils from Antarctica and Australia have added to our knowledge of the group. Corystosperms, Caytonia and Peltasperms Mesozoic seed ferns include several groups with frond-like leaves and seeds borne in cupules and relatively simple pollen organs. The corystosperms are characteristic of the Triassic of Gondwana, Caytonia of the Jurassic in various northern hemisphere localities, and the peltasperms in the Triassic of India and some other Gondwana localities. Corystosperms have frond-like leaves called Dicroidium which have a basal dichotomy and a widely varied frond morphology. They are somewhat leathery and amphistomatic.