The biology of Glossopteris: evidence from petrified seed-bearing and pollen-bearing organs

Silicified layers of plant material from the Late Permian Blackwater Group of the Bowen Basin, Queensland, contain seed-bearing organs associated with Glossopteris leaves; comparison of these organs with attached fertile glossopterid structures previously described from compressions indicates the petrified organs are undoubtedly of Glossopteris. The fructification consists of an infolded megasporophyll with loosely overlapping lateral margins forming an envelope bearing sessile gymnospermous seeds on the inner surface. The seeds contain a megagarnetophyte with one archegonium. Previous interpretations of fertile glossopterid structures as cupular valves, fertiligers, and cones with a subtending bract, e. g. Dictyopteridium and Scutum, are now reinterpreted as having a similar arrangement of megasporophyll envelope (= subtending bract of 'cone') enclosing the seeds. Pollen-bearing organs in the deposit are of the Arberiella type and contain bisaccate pollen. Similar pollen grains are found in the micropyles and pollen chambers of the seeds. Petrified fern leptosporangia are also common in the silicified material, but are not related to Glossopteris. Glossopteris, which was probably a deciduous aborescent gymnosperm, is considered to be a distinct type of pteridosperm.