What was the nature of plant life some 280 to 300 million years ago during the Coal Age? What kinds of plants contributed to the formation of midwestern coals? In what environments did those plants grow? These are the broad research questions that we have sought to answer.
Most of our efforts have been directed to the collection and study of petrified plant fossils, especially those present in subsperical masses of calcium carbonate and pyrite, which are commonly referred to as coal balls. Study of the cellular structure preserved in such fossils has enabled us to deduce details of the morphology, growth processes, reproductive biology, and ecological adaptations of Coal Age plants. Such insights have been useful in making taxonomic assignments of newly discovered forms, in understanding their evolutionary relationships, and in making paleoecological interpretations. We also have used quantitative estimates of the plant remains in coal balls and of the pollen and spores in the associated coals to recognize several distinct plant assemblages that we believe represent natural associations or communities.
Another exciting and productive area of research has involved petrified cycadeoid gymnosperms from the late Mesozoic of South Dakota. Our studies of the type specimens of Cycadeoidea dacotensis and C. McBridei have provided information on the complex vascularization of their cones and insights into the evolutionary origins of those structures and of diversification within the cycadeoids.
Most recently we have been involved in studying plant fossils from early carboniferous deposits in Iowa and cuticle material from a Devonian age paper coal.