Crepet, William , Stevenson, Dennis Wm. .
The Bennettittales (Cycadeoidales): a preliminary perspective on this arguably enigmatic group.
Most phylogenetic analyses based on morphological or structural characters have placed the Bennettitales comfortably within an anthophyte clade that includes the angiosperms and the Gnetales. The Bennettitales-Gnetales relationship has come into question because nucleic acid sequence-based phylogenies place the Gnetales with other gymnosperms outside of the anthophyte clade. Yet some recent morphology-based phylogenetic analyses reinstate the Gnetales as part of the anthophytes, reuniting them with the Bennettitales. Questions about a possible gnetalean-bennettitalean relationship are nothing new and have persisted since the early Twentieth Century. Some aspects of this controversy are examined in light of certain characters that may be inadequately understood or misrepresented in most existing phylogenetic analyses of morphological characters. Phylogenetic analysis of a morphology-based data set which reflects new characters or revised character codings removes Bennettitales from the anthophytes and places them in a latter day cycadofilicalean clade. While this analysis is preliminary and experimental in nature, it draws attention to the need for additional studies to clarify the nature and distribution of certain characters, especially the ovulate receptacles, if we are to determine more precisely and less subjectively the phylogenetic position of the Bennettitales and their relationship to the Gnetales and other seed plants.
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1 - Cornell University, Department of Plant Biology, 412 Mann LIbrary, Tower Road, Ithaca, NY, 14853, USA
2 - The New York Botanical Garden, 200th Street and Kazimiroff Blvd., Bronx, NY, 10458-5126
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Superior A/Cliff Lodge - Level C
Date: Wednesday, July 29th, 2009
Time: 9:30 AM