The power of two: Marrying phylogeny and biogeography to reconstruct the evolutionary history of pteridophytes
Gensel, Patricia G. , Skog, Judith E. .
A Paleobotanical Perspective On Fundamental Radiations In The Pteridophytes.
Recent phylogenetic analyses recognize two major lineages of tracheophytes. The fossil record indicates the lycophyte lineage probably originated as early as basal Silurian, given the presence of a variety of zosterophylls and Baragwanathia as early as the Ludlow (mid-late Silurian). Radiation of most lycopsids still appears to have occurred in the Devonian and lycophytes comprise major components of floras on most paleocontinents from Early Devonian times. The earliest fossil occurrence of the second tracheophyte lineage, termed euphyllophytes by Kenrick and Crane (1997), is Lower Devonian (Lochkovian? Pragian?) based on the presence of Psilophyton. Synapomorphies defining this clade, and some lineages in basal euphyllophytes, require further consideration, and transformations leading to ferns need clarification. Several lineages now included in euphyllophytes are implicated in evolution of both seed plants and other pteridophyte groups. The first undoubted filicalean ferns are known from Early Carboniferous strata, with radiation of several lineages through the Carboniferous, while undoubted seed plants date from the Late Devonian and also radiate during the Carboniferous. Geographic distribution of characters in the early euphyllophytes that relate to ferns and progymnosperms will be discussed in the context of their time of appearance, comparative prevalence, and possible relevance to fern evolution. A major question is whether the characters proposed to distinguish a ?fern-horsetail-Psilotophyte? lineage from a ?seed plant? lineage actually do so or if variants of these occur in both lineages.
1 - George Mason University, Department of Environmental Science and Policy 5F2, Fairfax, Virginia, 22030-4444, USA
2 - University of North Carolina, Biology Dept. CB#3280, Chapel Hill, North Carolina, 27599-3280
Presentation Type: Symposium
Location: Ballroom 1 (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 2:15 PM