Selena Smith University of Alberta Biological Sciences Edmonton Alberta T6G 2E9 Canada,Gar Rothwell Ohio University Environmental and Plant Biology Athens Ohio USA,Ruth Stockey University of Alberta Biological Sciences Edmonton Alberta Canada
British Columbia, Cretaceous, Cyathea cranhamii, Cyatheaceae, Filicales
Tree ferns occur throughout the world in predominantly tropical habitats. The
group has a long history and is known since the Jurassic, ca. 160 million
years ago. Fossils of this family, Cyatheaceae, are usually carbon imprints
(called compression fossils) of leaves. Other fossils, such as the stems
of tree ferns, are petrified, with the organic plant material mostly replaced
by minerals. This image of the indusium of Cyathea cranhamii Smith,
Rothwell et Stockey shows sporangia with spores. Spores are triangular with
a trilete mark. The sporangia have areas with thickened cell walls (the
annulus), which help in dehiscence (the opening of the sporangium) and spore
dispersal. Sporangial stalks are visible as small clusters of four to six
cells in cross section. Cyathea cranhamii comes from late Cretaceous
(ca. 130 million years ago) sediments of British Columbia, Canada and represents
the first known permineralized reproductive tree fern material.
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