STOCKEY, RUTH1* and GAR W. ROTHWELL2. 1Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada; 2Department of Environmental and Plant Biology, Ohio University, Athens, Ohio, 45701, USA. - Permineralized cycad seeds from the Jurassic of British Columbia, Canada.
Thirty three large seeds have been studied from cycad remains from
Jurassic sediments of South Balch Island (Queen Charlotte Islands) on
the west coast of Canada. Seventeen of the specimens range up to 6 cm
long and 5 cm in diameter, and conform to Cycadeocarpus
columbianus Dawson. The integument of these seeds consists of a
thick sarcotesta that surrounds a spongy zone of the integument that
is similar to the specialized flotation anatomy associated with water
dispersal in some living species of Cycas. However, radial
symmetry of these specimens is unlike the bilateral seeds produced by
living species of Cycas. These specimens also display a ring of
small teeth and associated oval channels surrounding the micropyle.
These form a structure that is similar to the coronula, a germination
mechanism common to many living cycad species. Five additional seed
specimens compare more favorably with living species of Cycas.
These seeds range to 5 cm long and 4 cm wide and are more-or-less
flattened in cross sections. A thick sarcotesta surrounds the stony
sclerotesta, with two longitudinally disposed sclerotestal ribs that
extend from near the micropyle to the chalaza. The nucellus is
confluent with the integument below the level of the pollen chamber.
These specimens display unique combinations of characters,
demonstrating both modern dispersal and germination mechanisms and
previously unknown diversity among Mesozoic cycads of North America.
Key words: Cycad, Dispersal, Fossil, Germination Biology, Jurassic, Seed