Paper No. 1
Presentation Time: 1:30 PM
DIVERSITY OF CRETACEOUS CONIFERS: A NEW SPECIES WITH POLLEN CONES THAT BEAR ADAXIAL POLLEN SACS AND POLLEN WITH FEATURES OF THE TAXODIACEOUS CONIFERS
Conifer-like plant organs are found in sediments dating back to the upper Carboniferous and are characterized by needle- or scale-like leaves with often isolated ovulate and pollen cones. These ancient conifers include the order Voltziales which diversifies throughout the Permian. Specimens assignable to modern groups date back to the Early Triassic and, at present, there are no synapomorphies that link the ancient Voltziales to modern conifers. Anatomically preserved conifer organs have been found in Lower Cretaceous (Barremian) marine carbonate nodules on Vancouver Island, Canada. Included are specimens assignable to the modern Cupressaceae, Pinaceae, and possibly other families. One conifer consists of shoots that bear unusual pollen cones with adaxial pollen sacs. 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. Several pollen sacs form a cluster in the midregion of the adaxial sporophyll surface. Pollen grains appear to be relatively immature as they are often found in tetrads. Pollen grains range 17 - 25 µm in diameter, are subspheroidal and nonsaccate. The exine consists of a thin nexine covered by a verrucate sexine with numerous scabrae, and, in these characters, is 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 possible phylogenetic link between some Voltziales and more recent families of the Coniferales. This conifer occurs much later than the Voltziales so its phylogenetic relationships remain unclear.