Koll, Rebecca , Manchester, Steven .
Taxonomic Relationships of Early and Middle Permian Gigantopterid Seed Plants in Western Pangea.
Gigantopterids, a group of Permian seed plants known for their distinctive herringbone venation pattern, may hold significant biogeographic and paleoenvironmental information tied closely to their stratigraphic distribution. Previous studies have outlined morphology through leaf venation and gross architecture of individual genera or groups of related species or genera but fail to address large-scale systematic or stratigraphic patterns of the entire clade. This study uses a comprehensive, multidisciplinary approach to define genera based on a suite of morphologic characteristics and patterns of morphologic variation. With this approach it is then possible to evaluate broader questions concerning paleoecology of gigantopterid distribution and the processes in which these plants invest energy (leaf economic spectrum or LES). The present study reports the results of a taxonomic investigation into the relationships of the several North American gigantopterid genera. Paleobotanical specimens analyzed as part of this study were collected between 1909-2013 by the US Geological Survey and US National Museum of Natural History (USNM) from strata of the Witchita, Bowie, Clear Fork and Pease River Groups of north-central Texas. Initial analysis of the literature and USNM collections indicates that variations in venation and subtle aspects of leaf shape reveal greater diversity in the North American gigantopterids than is presently understood, requiring reassessment of their relationships. Current literature suggests there are six major North American gigantopterid genera, however, morphologic analysis of the USNM collection has indicated the possibility of a taxonomic overlap of two previously defined genera: Gigantopteridium americanum and Cathaysiopteris yochelsonii. After compilation of morphologic features, including second and third order venation structure with margin character; it is believed that these genera comprise a gigantopterium-morphogroup, likely one genus with several intermediate species. Observations from the 2013 Texas field season show evidence of sedimentologic and pedogenic conditions suggesting a correlation of gigantopterid distributional patterns with environmental conditions and depositional settings. A preliminary assessment of the stratigraphic distribution of the gigantopterid group has indicated the possibility that each morphogroup may have dominated a unique niche of space and time in the Permian landscape.
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1 - University of Florida, Biology, Gainesville, FL, 32611, USA
2 - University of Florida, Florida Museum of Natural History, PO Box 117800, Gainesville, FL, 32611, USA
Western Equatorial Pangea.
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 28th, 2014
Time: 9:15 AM
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award