Stockey, Ruth , Escapa, Ignacio , Rothwell, Gar .
Two new Jurassic species of Pararaucaria (Cheirolepidiaceae) from Patagonia (Argentina) and Oregon (USA): dominance and extension of the Cheirolepidiaceae-Araucariaceae forests.
The genus Pararaucaria Wieland (Cheirolepidiaceae) was erected almost eighty years ago for seed cones from the famous Middle Jurassic Cerro Cuadrado locality (Santa Cruz Province, Argentina), where the specimens occur associated with Araucaria mirabilis. Early descriptions of the genus were followed by new descriptions and reinterpretations, but no new species were discovered and the systematic relationships of Pararaucaria remained equivocal. In an ongoing series of studies we have discovered that Pararaucaria patagonica represents the family Cheirolepidiaceae, and that two new species of Pararaucaria are present in the Late Jurassic Trowbridge Formation (Oregon, USA) and the Late Jurassic Canadon Calcareo Formation (Chubut Province, Argentina) respectively. Whereas, the Argentine fossils are preserved in a silica matrix like the type species, the Oregon cone occurs in a marine volcanoclastic carbonate concretion. Different preservational attributes of the three species provide complementary information about previously unknown or incompletely characterized features (e.g., distal branching of ovuliferous scale trace, number of seeds per bract/scale complex), and allow for a an improved understanding of the genus. All three species of Pararaucaria occur in association with seed cones assignable to the genus Araucaria, demonstrating the geographical and chronological extension of Cheirolepidaceae-Araucariaceae forest biomes from the Middle Jurassic to the Late Jurassic and from the Southern Hemisphere to the Northern Hemisphere.
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1 - Oregon State University, Department of Botany and Plant Pathology, 2082 Cordley Hall, Corvallis, OR, 97331, USA
2 - MEF-CONICET, Fontana 140, Trelew Chubut, N/A, 9100, Argentina
3 - Oregon State University, Department of Botany and Plant Pathology, 2082 Cordley Hall, Corvallis, OR, 97330, USA
conifer seed cone
Presentation Type: Oral Paper:Papers for Sections
Location: Union A/Hyatt
Date: Tuesday, July 10th, 2012
Time: 2:45 PM