Sanders, Heather , Rothwell, Gar W. , Stockey, Ruth A. .
Diversity of Cretaceous conifers: a species with pollen cones that bear adaxial pollen sacs
Large numbers of anatomically preserved conifers have been found in Lower Cretaceous (Hauterivian-Barremian) marine carbonate nodules on Vancouver Island, Canada. Included are specimens assignable to Cupressaceae, Pinaceae, and possibly other families. One conifer consists of shoots that produce unusual pollen cones with adaxial pollen sacs. These cones appear to have been preserved at differing developmental stages, including a relatively mature cone with pollen. Cones are borne laterally on vegetative branches that are characterized by helically arranged short needles. The mature cone is 7 mm long and 4 mm wide with helically arranged sporophylls. Sporophylls are triangular in cross section with tapering lateral margins. Radial sections of the cone show sporophylls that extend from the axis at an angle of about 90o, dip down and then turn upward at the apex. Sporophylls are thin at the base and more inflated distally. A large central resin canal extends from the axis to the apex of the sporophyll. Some sporophylls also display a resin canal abaxial to the large central canal. Up to four pollen sacs are borne in the midregion of the adaxial sporophyll surface. Some pollen sacs contain pollen grains that range 17 - 25 Ám in diameter, are subspheroidal and nonsaccate. The exine consists of a thin nexine covered by a verrucate sexine with numerous scabrae, similar to many species of the taxodiaceous Cupressaceae. These pollen cones differ from all modern conifers in the adaxial attachment of pollen sacs. However, they are similar to some Paleozoic and Triassic Voltziales in this character, suggesting a phylogenetic link between the Voltziales and more recent families of the Coniferales.
1 - Ohio University, Department of Environmental and Plant Biology, Porter Hall, Richland Avenue, Athens, Ohio, 45701-2979, USA
2 - University of Alberta, Department of Biological Sciences, CW 405 Biological Sciences Building, Edmonton, Alberta, T6G 2E9, Canada
adaxial pollen sacs.
Presentation Type: Paper
Location: Maybird (Cliff Lodge)
Date: Wednesday, August 4th, 2004
Time: 10:45 AM