Evolution Late Paleozoic conifers
The early conifers played a prominent role in the composition of xeric plant communities in the equatorial Euramerican province, which covered the southern part of the United States and Europe. These conifer species originated from more drier floras, which had co-existed with wetland vegetation for millions of years. The so-called 'walchian' conifers looked modern in general appearance, but were characterized by relatively simply organized female reproduction organs (fig. 1) and monosaccate prepollen. It has generally been inferred that the more derived families (Majonicaceae and Ullmanniaceae) known from the European Late Permian gradually evolved from the walchian conifers. These conifer taxa have bisaccate pollen, more complex female reproduction organs, and a more advanced reproduction strategy. Recent findings from Early to Middle Permian Lower Pease River Flora (fig. 2) in North-Central Texas, however, show that radiation in these conifer lineages occurred significantly earlier than previously thought. Studies on more taxonomically definitive structures, such as cuticles (fig. 3) and reproductive organs (fig. 4), is ongoing. In order to gain insight into the timing of origin and radiation of late Paleozoic conifers, and the role of changes in environmental conditions therein, megafossil and palynological research methods and environmental data are being integrated.
Looy, C.V., 2007. Extending the range of derived Late Paleozoic conifers: Lebowskia gen. nov. (Majonicaceae). International Journal of Plant Sciences 168: 57–972.