Ryberg, Patricia E. , Taylor, Edith L. .
A reassessment of permineralized glossopterid ovulate structures from the Central Transantarctic Mountains, Antarctica.
Permineralized ovulate structures have been known from the Late Permian Skaar Ridge locality of Antarctica for several decades, but a comprehensive description has never been provided. Previous studies on Skaar Ridge ovulate structures have presented two distinctive structures. With new material, these two morphologies can be shown to belong to a single genus. The structure is a multiovulate megasporophyll with recurved margins and no distinctive midrib. The vasculature of the sporophyll consists of xylem with scalariform thickenings and lacunae in the position of phloem. Transfusion tracheids with scalariform thickenings are found throughout the mesophyll. Specimens represent marginal sections of the sporophyll and thin filaments that appear between each ovule may be a remnant of the recurved margin of the sporophyll, since none of the sections definitively show the ovules being completely enclosed in the filaments. Ovules are attached by a short stalk to the adaxial surface of the megasporophyll. Vasculature from the sporophyll enters the stalk and terminates in the chalazal end of the ovule. Ovules are orthotropous, have two wings and an elaborated sclerotesta at the micropylar end. Inner cells of the sclerotesta form lignified parenchyma cells into two appressed hemispheres of tissue with a small opening between them forming the micropyle and pollen chamber. Outer cells of the sclerotesta arch over the parenchyma mass with thick walled cells creating a chamber above the micropyle. The nucellus is free except at the base of the ovule. The distinctive features of this genus of glossopterid ovulate structure are compared to both impression and permineralized material of glossopterid structures from throughout Gondwana.
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1 - University of Kansas, Department of Ecology & Evolutionary Biology, Natural History Museum and Biodiversity Research Center, 1200 Sunnyside Avenue, Lawrence, Kansas, 66045-7534, USA
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Superior A/Cliff Lodge - Level C
Date: Monday, July 27th, 2009
Time: 9:45 AM