Rothwell, Gar W. , Stockey, Ruth A. .
The evolution of gnetophytes, Lower Cretaceous evidence from an anatomically preserved seed cone.
Among the exceptionally rich flora of anatomically preserved plants that occur within carbonate marine concretions from the Lower Cretaceous (Valanginian/Hauterivian boundary) at Apple Bay on Vancouver Island, BC, Canada, are abundant seed plants assignable to seed ferns, Bennettitales, and several families of Coniferales. A well preserved seed cone with attached ovules expands that diversity to the Gnetales. The cone consists of a primary axis that bears opposite/decussate bracts with axillary secondary shoots. Each secondary shoot produces two decussate pairs of bracteoles below two erect ovules. Ovules consist of a multiseriate integument that displays the radially elongated inner epidermal cells that characterize the most apical region of the micropylar canal in other living and extinct Gnetales. The nucellus is attached to the integument in the chalazal region and free distally, with a prominent pollen chamber. Several features of this new seed cone conform to the ancestral character states for Ephedra hypothesized by Eames more than 50 years ago, including two ovules per secondary shoot, bracteoles that do not enclose the ovules, and the absence of a tubular micropyle.
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1 - Ohio University, Department of Environmental & Plant Biology, Porter Hall, Richland Avenue, Athens, Ohio, 45701-2979, USA
2 - University of Alberta, Department of Biological Sciences, Biological Sciences Centre, Cw 405, Edmonton, Alberta, T6G 2E9, Canada
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Superior A/Cliff Lodge - Level C
Date: Wednesday, July 29th, 2009
Time: 10:30 AM