A century of seed ferns: A symposium to celebrate paradigm shifts in the understanding of seed plant
Taylor, Edith L. , Taylor, Thomas N. .
The Mesozoic seed ferns: Old ideas, new discoveries.
The Mesozoic seed ferns are a loose conglomeration of gymnospermous plants whose affinities continue to remain problematic. The three major orders recognized today are the Caytoniales (Triassic-Cretaceous), Peltaspermales (Permian-Triassic) and Corystospermales (Triassic). There are various miscellaneous genera described from Mesozoic rocks that could also be included in the Mesozoic seed ferns, but their frequency and distribution precludes their assignment to specific orders. The plants in the three principal orders have been important in phylogenetic analyses of seed plants and have been implicated as angiosperm progenitors at various times in the past. All three groups were originally described from compression/impression fossils only, but anatomically preserved corystosperms are now known from Argentina and Antarctica. Since their original description, their geographic ranges have expanded, such that members of all three groups are known to occur in both the northern and southern hemispheres. This paper will summarize our current knowledge of the Mesozoic seed ferns and the phylogenetic position of the three orders within the seed plants, focusing especially on permineralized and compressed corystosperms from the Triassic of Antarctica. Despite repeated attempts to homologize various organs, the origins of the corystosperms and their relationship to other seed plants have changed little since H. Hamshaw Thomas first established the group in 1933. Recent studies of well-preserved material from the central Transantarctic Mountains have provided information about the three-dimensional morphology and anatomy of pollen organs and ovulate cupules, as well as the first evidence of the attachment of reproductive organs to the parent plant. These discoveries provide new information that can be used in phylogenetic analyses to provide increased resolution of seed plant evolution.
1 - University of Kansas, Dept. Ecol. & Evol. Biol. and Natural History Museum, 1200 Sunnyside Ave., Lawrence, Kansas, 66045-7534, USA
Mesozoic seed ferns
seed plant evolution
Presentation Type: Symposium
Location: Ballroom 1 (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 9:15 AM