Stockey, Ruth A. , Rothwell, Gar W. .
In search of the first flowering plants: permineralized vegetation from the Valanginian/Hauterivian boundary on Vancouver Island, Canada.
A remarkably diverse Lower Cretaceous (Valanginian-Hauterivian) flora at Apple Bay on Vancouver Island includes seed plants at an important time of evolutionary and floristic transition. Carbonate marine nodules yield plants that are preserved in three dimensional and anatomical detail. Older floras are dominated by ferns, equisetophytes other pteridophytes, as well as by gymnosperms including conifers, gnetophytes, cycadophytes, and seed ferns. Angiosperms and several modern families of gymnosperms first enter the fossil record at this important floristic transition. Among the seed plants at Apple Bay are conifers of modern families (Pinaceae, Cupressaceae), and conifers similar to extinct Voltziales based on the structure of pollen cones. The pollen record includes “ Clavatipollenites ”-type pollen, a palynomorph found on early chloranthaceous fruits. Other gymnospermous remains include cycadophyte leaves and reproductive structures comprised of aggregations of seeds similar to Carnoconites (Pentoxylales) with embryos and micropyles like seeds of the Bennettitales. Some of the most exciting fossils consist of a single pyramidal seed enclosed within a cupule- or carpel-like structure that probably represents a seed fern. Seeds are 2-3 mm in diameter and 3 mm long with an integument 4-8 cells thick of small parenchymatous cells on the flat sides that increase to 24-28 cells in the angles (corners). Each seed is completely surrounded by a cupule, 3-4 mm in diameter, up to 5.5 mm long. Cupules are composed of elongate sclereids with spiral thickenings that grade externally to a few rows of parenchyma. The cupules have one vascular bundle and lack trichomes. Triangular seeds are similar to those of the Triassic seed fern Petriellaea but are about 100 million years younger and differ from Petriellaea by having only one seed per cupule. Confirmation of these plants as seed ferns, makes them some of the youngest representatives of this systematic grade.
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1 - University of Alberta, Department of Biological Sciences, Biological Sciences Centre, Cw 405, Edmonton, Alberta, T6G 2E9, Canada
2 - Ohio University, Department of Environmental & Plant Biology, Porter Hall, Richland Avenue, Athens, Ohio, 45701-2979, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Lake Erie/Hilton
Date: Tuesday, July 10th, 2007
Time: 9:00 AM