A century of seed ferns: A symposium to celebrate paradigm shifts in the understanding of seed plant
DiMichele, William , Phillips, Tom , Pfefferkorn, Hermann .
The Paleoecology of Permo-Carboniferous Pteridosperms.
Permo-Carboniferous "seed ferns" were a phylogenetically disparate group, including the medullosans, lyginopterids, callistophytaleans, and, by some definitions, the peltasperms, gigantopterids and others. The former groups were abundant in the Euramerican tropical wetland biome. Peltasperms and gigantopterids occurred in Euramerica, Cathaysia and Angara, in the seasonally-dry biome.
Within the wetlands, pteridosperms were abundant and diverse in clastic, floodbasin environments. In peat-forming habitats they were subdominant, preferring fire- and flood-prone settings, indicated by association with mineral matter and charcoal. No medullosan (foliage) species were unique to peat-substrates but were a subset of the larger range of medullosan diversity. Peltasperms were a dominant element of seasonally-dry habitats. This group became diverse and important in Early Permian flood plains, possibly in wetter streamsides, appearing in similar environments during the Late Permian in the Angaran floral province. Gigantopterids were minor components of flood-plain vegetation.
Medullosans were free-standing trees, thicket-forming shrubs, and vines, locally canopy dominants and substory elements in lycopsid and tree-fern forests. Callistophytaleans and lyginopterids were primarily lianas and scrambling forms, the latter occasionally dominant. Peltasperms were likely small trees based on leaf/frond morphology. Gigantopterids were likely vines and small shrubs.
Reproductively, the most peculiar aspects of the medullosans were the large sizes of the ovules and pollen grains in some species, leading to suggestions of insect or water pollination and animal seed dispersal. Callistophyton and Lyginopteris had both small seeds and prepollen with wind pollination and several possible means of seed dispersal. Gigantopterids and peltasperms may have been wind pollinated and dispersed.
Pteridosperms were abundant and widespread in the late Paleozoic, largely as ecological specialists rather than weedy generalists. As trees, shrubs, and vines, the pteridosperms were important in nearly all wet tropical habitats, other than those with standing water. Some lineages were important in seasonally dry environments through the Late Permian.
1 - Smithsonian Institution, Department of Paleobiology, MRC121 NHB, Washington, DC, 20560, USA
2 - University of Illinois, Department of Plant Biology, 265 Morrill Hall, Urbana, Illinois, 61801
3 - University of Pennsylvania, Department of Earth and Environmental Sciences, Philadelphia, Pennsylvania, 19104, USA
Presentation Type: Symposium
Location: Ballroom 1 (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 10:00 AM