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The morphology and anatomy of fern reproductive organs has traditionally been of great importance in determining both pteridophyte classification and phylogeny. Much of the diversification and radiation of the Filicales relative to extant families occurred during the Mesozoic, and several permineralized and compressed specimens of modern groups have been described from the Triassic and Jurassic of Antarctica. Many of these are from primitive groups including members of the Marattiales and Osmundaceae (Triassic) as well as others such as the Dipteridaceae (Jurassic). A cluster of permineralized sporangia has recently been discovered from the Fremouw Formation of the Triassic of Antarctica. Sporangia are leptosporangiate, average 350 [[micro]meter] in diameter, and have an apical/vertical annulus that is up to 11 cells in length. Sporangia are attached to a poorly preserved foliar unit by a short stalk that is approximately 10 - 15 cells wide and 65 [[micro]meter] in length; stalks appear to terminate in a receptacle-like structure. Spores are trilete, subtriangular and are approximately 30 [[micro]meter] in diameter. Small spherical bodies are also present in the sporangia which may be tapetal remnants or fungal spores. The thickness of the sporangial stalk suggests that these sporangia are primitive among leptosporangiate ferns. The sporangial structure appears similar to that of Paleozoic families such as Tedeleaceae; the combination of sporangial and spore characters present suggests affinities with the modern family Schizaeaceae and to the family Cynepteridaceae from the Triassic of North America.