ROTHWELL, GAR W.1* and RUTH STOCKEY2. 1Department of Environmental and Plant Biology, Ohio University, Athens, Ohio, 45701, USA; 2Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada. - Systematic characters of ovulate Cycadeoidea/Bennettites cones from the Cretaceous of Vancouver and Hornby Islands, British Columbia, Canada.
Four fragments of anatomically preserved ovulate cycadeoid cones have
been recovered from Upper Cretaceous (Santonian-Campanian) sediments
of Vancouver and Hornby Islands, British Columbia, Canada. All of the
specimens consist of tightly packed interseminal scales and ovulate
sporophylls with terminal ovules. One specimen also preserves remains
of a small receptacle. Interseminal scales and ovulate sporophylls are
oriented more-or-less parallel to one another. Ovules are distinctly
stellate proximal to the tubular micropyle, and the sarcotesta
consists of longitudinally oriented tubular cells that are attached to
the sclerotesta only at the apex. The vascular strand below the base
of each ovule is highly contorted in a pattern characteristic of
contractile tissue in some living plants, and this provides evidence
for some post-pollination facets of reproductive biology. These cones
are quite similar to Bennettites gibsonianus Carruthers,
Bennettites morierei (Saporta and Marion) Lignier,
Bennettites albianus Stopes, and several species of ovulate
Cycadeoidea as described by Wieland. The superb preservation of
these and other cones from Vancouver Island demonstrates that
Cycadeoidales/Bennettitales lack a cupule, have radial seeds, have
nucellar vascular tissue (but no integumentary tracheids), and that no
pollen chamber is produced. Together with a Williamsonia
preserved in the same deposits, these specimens also provide a clear
set of contrasting systematic characters for differentiating between
isolated cones of the Williamsoniaceae and Cycadeoidaceae.
Key words: Bennettitales, Cretaceous, Cycadeoidales, Seed Cones